Vulnerability-Lookup

CVE-2026-80926 (GCVE-0-2026-80926)

Vulnerability from cvelistv5 – Published: 2026-09-11 19:37 – Updated: 2026-09-13 06:28

Title

ksmbd: fix use-after-free in oplock break notification

Summary

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix use-after-free in oplock break notification smb2_oplock_break_noti() reads opinfo->conn without any lock and dereferences it after two allocations which may sleep. When the durable handle owning the oplock is disconnected, session_fd_check() clears opinfo->conn and drops its conn reference under ci->m_lock, and the last ksmbd_conn_put() frees the connection. A break triggered by another connection that races with the teardown can then resurrect the freed connection: ksmbd_conn_get() is a plain atomic_inc, and the queued break work later dereferences the stale conn via ksmbd_conn_write(), a use-after-free reachable by any authenticated client holding a durable batch oplock. Thread the caller's inode into the notification path instead of taking a new reference on it. Every caller of oplock_break() already holds a live ksmbd_file (or an explicit ksmbd_inode_lookup_lock() reference, in the parent lease break paths) on the inode that owns the break target's oplock list, so ci cannot be freed during the call, and its lock can be taken without dereferencing opinfo->o_fp, which a concurrent close may free. Select and pin the connection under ci->m_lock, the same lock session_fd_check() and ksmbd_reopen_durable_fd() use to update opinfo->conn, so a concurrent detach either loses the race to the clear or keeps the connection alive until the notification work releases it. Transfer the reference to the work item and release it on allocation failures.

Severity

9.8 (Critical)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Assigner

Linux mitre root

References

3 references

URL	Tags
https://git.kernel.org/stable/c/c8279ae8df68cce9c…
https://git.kernel.org/stable/c/8cc98db4fc590e6c7…
https://git.kernel.org/stable/c/0e753899627b5e28a…

Impacted products

2 products

Vendor	Product	Version	CPE status
Linux	Linux	Affected: e735dbd489e3ea02be78dba991056fe1138be51e , < c8279ae8df68cce9cd3b785e85f7a86c80a46e78 (git) Affected: b003086d76968298f22e7cf62239833b5a3a06b1 , < 8cc98db4fc590e6c7d9db6529320982ee16c5d1d (git) Affected: b003086d76968298f22e7cf62239833b5a3a06b1 , < 0e753899627b5e28a9fea8bca98262a6f65a2452 (git) Affected: 945a86b21b40fb17183f5b27461baa6f03e2467f (git) Affected: 1ff58dcfcab434ebb51649da33774fbb8e1f7b67 (git) Affected: 75e33deda658c1ab3a9336cbdb1436536f9b3660 (git) Affected: 6.18.36 , < 6.18.51 (semver) Affected: 6.6.143 , < 6.7 (semver) Affected: 6.12.94 , < 6.13 (semver) Affected: 7.0.13 , < 7.1 (semver)	guessed
Linux	Linux	Affected: 7.1 Unaffected: 0 , < 7.1 (semver) Unaffected: 6.18.51 , ≤ 6.18.* (semver) Unaffected: 7.2.5 , ≤ 7.2.* (semver) Unaffected: 7.3-rc2 , ≤ * (original_commit_for_fix)	guessed

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/server/oplock.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "c8279ae8df68cce9cd3b785e85f7a86c80a46e78",
              "status": "affected",
              "version": "e735dbd489e3ea02be78dba991056fe1138be51e",
              "versionType": "git"
            },
            {
              "lessThan": "8cc98db4fc590e6c7d9db6529320982ee16c5d1d",
              "status": "affected",
              "version": "b003086d76968298f22e7cf62239833b5a3a06b1",
              "versionType": "git"
            },
            {
              "lessThan": "0e753899627b5e28a9fea8bca98262a6f65a2452",
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              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "945a86b21b40fb17183f5b27461baa6f03e2467f",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "1ff58dcfcab434ebb51649da33774fbb8e1f7b67",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "75e33deda658c1ab3a9336cbdb1436536f9b3660",
              "versionType": "git"
            },
            {
              "lessThan": "6.18.51",
              "status": "affected",
              "version": "6.18.36",
              "versionType": "semver"
            },
            {
              "lessThan": "6.7",
              "status": "affected",
              "version": "6.6.143",
              "versionType": "semver"
            },
            {
              "lessThan": "6.13",
              "status": "affected",
              "version": "6.12.94",
              "versionType": "semver"
            },
            {
              "lessThan": "7.1",
              "status": "affected",
              "version": "7.0.13",
              "versionType": "semver"
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        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/server/oplock.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "7.1"
            },
            {
              "lessThan": "7.1",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.51",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.5",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3-rc2",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.51",
                  "versionStartIncluding": "6.18.36",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.5",
                  "versionStartIncluding": "7.1",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3-rc2",
                  "versionStartIncluding": "7.1",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionStartIncluding": "6.6.143",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionStartIncluding": "6.12.94",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionStartIncluding": "7.0.13",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: fix use-after-free in oplock break notification\n\nsmb2_oplock_break_noti() reads opinfo-\u003econn without any lock and\ndereferences it after two allocations which may sleep.  When the\ndurable handle owning the oplock is disconnected, session_fd_check()\nclears opinfo-\u003econn and drops its conn reference under ci-\u003em_lock, and\nthe last ksmbd_conn_put() frees the connection.  A break triggered by\nanother connection that races with the teardown can then resurrect the\nfreed connection: ksmbd_conn_get() is a plain atomic_inc, and the\nqueued break work later dereferences the stale conn via\nksmbd_conn_write(), a use-after-free reachable by any authenticated\nclient holding a durable batch oplock.\n\nThread the caller\u0027s inode into the notification path instead of taking\na new reference on it.  Every caller of oplock_break() already holds a\nlive ksmbd_file (or an explicit ksmbd_inode_lookup_lock() reference,\nin the parent lease break paths) on the inode that owns the break\ntarget\u0027s oplock list, so ci cannot be freed during the call, and its\nlock can be taken without dereferencing opinfo-\u003eo_fp, which a\nconcurrent close may free.  Select and pin the connection under\nci-\u003em_lock, the same lock session_fd_check() and\nksmbd_reopen_durable_fd() use to update opinfo-\u003econn, so a concurrent\ndetach either loses the race to the clear or keeps the connection\nalive until the notification work releases it.  Transfer the reference\nto the work item and release it on allocation failures."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 9.8,
            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - ksmbd is the in-kernel SMB server on TCP/445; smb2_oplock_break_noti() is reached from remote SMB2 CREATE/WRITE/truncate that breaks a durable batch oplock, and the racing teardown is a remote disconnect or SMB2 LOGOFF, so a network peer fully drives the UAF.\nAC:L - The attacker controls both sides of the race: one connection holds a durable batch oplock while a second opens the same file to force oplock_break(), and dropping the first connection runs session_fd_check() during the sleeping allocations before ksmbd_conn_get(); the window is retryable.\nPR:N - ksmbd shares are commonly exposed with guest/anonymous mapping, so a remote client can SESSION_SETUP, TREE_CONNECT, CREATE a durable batch oplock, and trigger the racing disconnect without a privileged host account; no meaningful credential gate protects this path.\nUI:N - No victim action is required; the attacker opens both SMB connections, requests the durable batch oplock, forces the conflicting open, and drops the first connection entirely on their own.\nS:U - The freed ksmbd_conn and resulting kernel heap corruption stay within the ksmbd/kernel security authority on the SMB server host; this is not a VM, IOMMU, or sandbox escape.\nC:H - Use-after-free of struct ksmbd_conn lets the attacker reclaim the slab object; __smb2_oplock_break_noti() then reads conn-\u003etransport and related fields from attacker-controlled memory, enabling kernel pointer and data disclosure.\nI:H - ksmbd_conn_write() calls conn-\u003etransport-\u003eops-\u003ewritev and ksmbd_conn_lock() on the freed object, so heap spraying the reclaimed ksmbd_conn yields an arbitrary function-pointer call and mutex writes into attacker-chosen memory.\nA:H - Even without a fully controlled exploit, using a freed ksmbd_conn (mutex lock, transport dereference, r_count/waitqueue) causes kernel memory corruption, oops, or panic and takes down the host."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-13T06:28:07.655Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/c8279ae8df68cce9cd3b785e85f7a86c80a46e78"
        },
        {
          "url": "https://git.kernel.org/stable/c/8cc98db4fc590e6c7d9db6529320982ee16c5d1d"
        },
        {
          "url": "https://git.kernel.org/stable/c/0e753899627b5e28a9fea8bca98262a6f65a2452"
        }
      ],
      "title": "ksmbd: fix use-after-free in oplock break notification",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-80926",
    "datePublished": "2026-09-11T19:37:29.855Z",
    "dateReserved": "2026-08-26T14:34:25.802Z",
    "dateUpdated": "2026-09-13T06:28:07.655Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-80926",
      "date": "2026-09-12",
      "epss": "0.00166",
      "percentile": "0.06127"
    },
    "microsoft_vex": {
      "current_release_date": "2026-09-13T01:05:15.000Z",
      "cve": "CVE-2026-80926",
      "id": "msrc_CVE-2026-80926",
      "initial_release_date": "2026-09-13T01:05:15.000Z",
      "product_status:under_investigation": "1",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "ksmbd: fix use-after-free in oplock break notification",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-80926.json",
      "version": "1"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-80926\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-09-11T20:18:56.257\",\"lastModified\":\"2026-09-13T07:16:59.460\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nksmbd: fix use-after-free in oplock break notification\\n\\nsmb2_oplock_break_noti() reads opinfo-\u003econn without any lock and\\ndereferences it after two allocations which may sleep.  When the\\ndurable handle owning the oplock is disconnected, session_fd_check()\\nclears opinfo-\u003econn and drops its conn reference under ci-\u003em_lock, and\\nthe last ksmbd_conn_put() frees the connection.  A break triggered by\\nanother connection that races with the teardown can then resurrect the\\nfreed connection: ksmbd_conn_get() is a plain atomic_inc, and the\\nqueued break work later dereferences the stale conn via\\nksmbd_conn_write(), a use-after-free reachable by any authenticated\\nclient holding a durable batch oplock.\\n\\nThread the caller\u0027s inode into the notification path instead of taking\\na new reference on it.  Every caller of oplock_break() already holds a\\nlive ksmbd_file (or an explicit ksmbd_inode_lookup_lock() reference,\\nin the parent lease break paths) on the inode that owns the break\\ntarget\u0027s oplock list, so ci cannot be freed during the call, and its\\nlock can be taken without dereferencing opinfo-\u003eo_fp, which a\\nconcurrent close may free.  Select and pin the connection under\\nci-\u003em_lock, the same lock session_fd_check() and\\nksmbd_reopen_durable_fd() use to update opinfo-\u003econn, so a concurrent\\ndetach either loses the race to the clear or keeps the connection\\nalive until the notification work releases it.  Transfer the reference\\nto the work item and release it on allocation failures.\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"fs/smb/server/oplock.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"e735dbd489e3ea02be78dba991056fe1138be51e\",\"lessThan\":\"c8279ae8df68cce9cd3b785e85f7a86c80a46e78\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"b003086d76968298f22e7cf62239833b5a3a06b1\",\"lessThan\":\"8cc98db4fc590e6c7d9db6529320982ee16c5d1d\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"b003086d76968298f22e7cf62239833b5a3a06b1\",\"lessThan\":\"0e753899627b5e28a9fea8bca98262a6f65a2452\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"945a86b21b40fb17183f5b27461baa6f03e2467f\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"1ff58dcfcab434ebb51649da33774fbb8e1f7b67\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"75e33deda658c1ab3a9336cbdb1436536f9b3660\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"6.18.36\",\"lessThan\":\"6.18.51\",\"versionType\":\"semver\",\"status\":\"affected\"},{\"version\":\"6.6.143\",\"lessThan\":\"6.7\",\"versionType\":\"semver\",\"status\":\"affected\"},{\"version\":\"6.12.94\",\"lessThan\":\"6.13\",\"versionType\":\"semver\",\"status\":\"affected\"},{\"version\":\"7.0.13\",\"lessThan\":\"7.1\",\"versionType\":\"semver\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"fs/smb/server/oplock.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"7.1\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"7.1\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.18.51\",\"lessThanOrEqual\":\"6.18.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.2.5\",\"lessThanOrEqual\":\"7.2.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.3-rc2\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H\",\"baseScore\":9.8,\"baseSeverity\":\"CRITICAL\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":3.9,\"impactScore\":5.9}]},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/0e753899627b5e28a9fea8bca98262a6f65a2452\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/8cc98db4fc590e6c7d9db6529320982ee16c5d1d\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/c8279ae8df68cce9cd3b785e85f7a86c80a46e78\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}

FKIE_CVE-2026-80926

Vulnerability from fkie_nvd - Published: 2026-09-11 20:18 - Updated: 2026-09-13 07:16

Severity

9.8 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Summary

References

	URL	Tags
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/0e753899627b5e28a9fea8bca98262a6f65a2452
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/8cc98db4fc590e6c7d9db6529320982ee16c5d1d
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/c8279ae8df68cce9cd3b785e85f7a86c80a46e78

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/server/oplock.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "c8279ae8df68cce9cd3b785e85f7a86c80a46e78",
              "status": "affected",
              "version": "e735dbd489e3ea02be78dba991056fe1138be51e",
              "versionType": "git"
            },
            {
              "lessThan": "8cc98db4fc590e6c7d9db6529320982ee16c5d1d",
              "status": "affected",
              "version": "b003086d76968298f22e7cf62239833b5a3a06b1",
              "versionType": "git"
            },
            {
              "lessThan": "0e753899627b5e28a9fea8bca98262a6f65a2452",
              "status": "affected",
              "version": "b003086d76968298f22e7cf62239833b5a3a06b1",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "945a86b21b40fb17183f5b27461baa6f03e2467f",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "1ff58dcfcab434ebb51649da33774fbb8e1f7b67",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "75e33deda658c1ab3a9336cbdb1436536f9b3660",
              "versionType": "git"
            },
            {
              "lessThan": "6.18.51",
              "status": "affected",
              "version": "6.18.36",
              "versionType": "semver"
            },
            {
              "lessThan": "6.7",
              "status": "affected",
              "version": "6.6.143",
              "versionType": "semver"
            },
            {
              "lessThan": "6.13",
              "status": "affected",
              "version": "6.12.94",
              "versionType": "semver"
            },
            {
              "lessThan": "7.1",
              "status": "affected",
              "version": "7.0.13",
              "versionType": "semver"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/server/oplock.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "7.1"
            },
            {
              "lessThan": "7.1",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.51",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.5",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3-rc2",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: fix use-after-free in oplock break notification\n\nsmb2_oplock_break_noti() reads opinfo-\u003econn without any lock and\ndereferences it after two allocations which may sleep.  When the\ndurable handle owning the oplock is disconnected, session_fd_check()\nclears opinfo-\u003econn and drops its conn reference under ci-\u003em_lock, and\nthe last ksmbd_conn_put() frees the connection.  A break triggered by\nanother connection that races with the teardown can then resurrect the\nfreed connection: ksmbd_conn_get() is a plain atomic_inc, and the\nqueued break work later dereferences the stale conn via\nksmbd_conn_write(), a use-after-free reachable by any authenticated\nclient holding a durable batch oplock.\n\nThread the caller\u0027s inode into the notification path instead of taking\na new reference on it.  Every caller of oplock_break() already holds a\nlive ksmbd_file (or an explicit ksmbd_inode_lookup_lock() reference,\nin the parent lease break paths) on the inode that owns the break\ntarget\u0027s oplock list, so ci cannot be freed during the call, and its\nlock can be taken without dereferencing opinfo-\u003eo_fp, which a\nconcurrent close may free.  Select and pin the connection under\nci-\u003em_lock, the same lock session_fd_check() and\nksmbd_reopen_durable_fd() use to update opinfo-\u003econn, so a concurrent\ndetach either loses the race to the clear or keeps the connection\nalive until the notification work releases it.  Transfer the reference\nto the work item and release it on allocation failures."
    }
  ],
  "id": "CVE-2026-80926",
  "lastModified": "2026-09-13T07:16:59.460",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 9.8,
          "baseSeverity": "CRITICAL",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 5.9,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-09-11T20:18:56.257",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/0e753899627b5e28a9fea8bca98262a6f65a2452"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/8cc98db4fc590e6c7d9db6529320982ee16c5d1d"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/c8279ae8df68cce9cd3b785e85f7a86c80a46e78"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}

GHSA-4R76-CQQC-V36J

Vulnerability from github – Published: 2026-09-11 21:31 – Updated: 2026-09-13 09:32

Details

In the Linux kernel, the following vulnerability has been resolved:

ksmbd: fix use-after-free in oplock break notification

smb2_oplock_break_noti() reads opinfo->conn without any lock and dereferences it after two allocations which may sleep. When the durable handle owning the oplock is disconnected, session_fd_check() clears opinfo->conn and drops its conn reference under ci->m_lock, and the last ksmbd_conn_put() frees the connection. A break triggered by another connection that races with the teardown can then resurrect the freed connection: ksmbd_conn_get() is a plain atomic_inc, and the queued break work later dereferences the stale conn via ksmbd_conn_write(), a use-after-free reachable by any authenticated client holding a durable batch oplock.

Thread the caller's inode into the notification path instead of taking a new reference on it. Every caller of oplock_break() already holds a live ksmbd_file (or an explicit ksmbd_inode_lookup_lock() reference, in the parent lease break paths) on the inode that owns the break target's oplock list, so ci cannot be freed during the call, and its lock can be taken without dereferencing opinfo->o_fp, which a concurrent close may free. Select and pin the connection under ci->m_lock, the same lock session_fd_check() and ksmbd_reopen_durable_fd() use to update opinfo->conn, so a concurrent detach either loses the race to the clear or keeps the connection alive until the notification work releases it. Transfer the reference to the work item and release it on allocation failures.

Severity

9.8 (Critical)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Show details on source website

JSON

To clipboard

{
  "affected": [],
  "aliases": [
    "CVE-2026-80926"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-09-11T20:18:56Z",
    "severity": "CRITICAL"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: fix use-after-free in oplock break notification\n\nsmb2_oplock_break_noti() reads opinfo-\u003econn without any lock and\ndereferences it after two allocations which may sleep.  When the\ndurable handle owning the oplock is disconnected, session_fd_check()\nclears opinfo-\u003econn and drops its conn reference under ci-\u003em_lock, and\nthe last ksmbd_conn_put() frees the connection.  A break triggered by\nanother connection that races with the teardown can then resurrect the\nfreed connection: ksmbd_conn_get() is a plain atomic_inc, and the\nqueued break work later dereferences the stale conn via\nksmbd_conn_write(), a use-after-free reachable by any authenticated\nclient holding a durable batch oplock.\n\nThread the caller\u0027s inode into the notification path instead of taking\na new reference on it.  Every caller of oplock_break() already holds a\nlive ksmbd_file (or an explicit ksmbd_inode_lookup_lock() reference,\nin the parent lease break paths) on the inode that owns the break\ntarget\u0027s oplock list, so ci cannot be freed during the call, and its\nlock can be taken without dereferencing opinfo-\u003eo_fp, which a\nconcurrent close may free.  Select and pin the connection under\nci-\u003em_lock, the same lock session_fd_check() and\nksmbd_reopen_durable_fd() use to update opinfo-\u003econn, so a concurrent\ndetach either loses the race to the clear or keeps the connection\nalive until the notification work releases it.  Transfer the reference\nto the work item and release it on allocation failures.",
  "id": "GHSA-4r76-cqqc-v36j",
  "modified": "2026-09-13T09:32:08Z",
  "published": "2026-09-11T21:31:19Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-80926"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/0e753899627b5e28a9fea8bca98262a6f65a2452"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/8cc98db4fc590e6c7d9db6529320982ee16c5d1d"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/c8279ae8df68cce9cd3b785e85f7a86c80a46e78"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}

MSRC_CVE-2026-80926

Vulnerability from csaf_microsoft - Published: 2026-09-13 01:05 - Updated: 2026-09-13 01:05

Summary

ksmbd: fix use-after-free in oplock break notification

Notes

Additional Resources: To determine the support lifecycle for your software, see the Microsoft Support Lifecycle: https://support.microsoft.com/lifecycle

Disclaimer: The information provided in the Microsoft Knowledge Base is provided \"as is\" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.

CVE-2026-80926

Affected products

Under investigation 1 product

Product	Identifier	Version	Remediation
Unresolved product id: 17084-1		—

References

4 references

URL	Category
https://msrc.microsoft.com/csaf/vex/2026/msrc_cve…	self
https://support.microsoft.com/lifecycle	external
https://www.first.org/cvss	external
https://msrc.microsoft.com/csaf/vex/2026/msrc_cve…	self

JSON

To clipboard

{
  "document": {
    "category": "csaf_vex",
    "csaf_version": "2.0",
    "distribution": {
      "text": "Public",
      "tlp": {
        "label": "WHITE",
        "url": "https://www.first.org/tlp/"
      }
    },
    "lang": "en-US",
    "notes": [
      {
        "category": "general",
        "text": "To determine the support lifecycle for your software, see the Microsoft Support Lifecycle: https://support.microsoft.com/lifecycle",
        "title": "Additional Resources"
      },
      {
        "category": "legal_disclaimer",
        "text": "The information provided in the Microsoft Knowledge Base is provided \\\"as is\\\" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.",
        "title": "Disclaimer"
      }
    ],
    "publisher": {
      "category": "vendor",
      "contact_details": "secure@microsoft.com",
      "name": "Microsoft Security Response Center",
      "namespace": "https://msrc.microsoft.com"
    },
    "references": [
      {
        "category": "self",
        "summary": "CVE-2026-80926 ksmbd: fix use-after-free in oplock break notification - VEX",
        "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-80926.json"
      },
      {
        "category": "external",
        "summary": "Microsoft Support Lifecycle",
        "url": "https://support.microsoft.com/lifecycle"
      },
      {
        "category": "external",
        "summary": "Common Vulnerability Scoring System",
        "url": "https://www.first.org/cvss"
      }
    ],
    "title": "ksmbd: fix use-after-free in oplock break notification",
    "tracking": {
      "current_release_date": "2026-09-13T01:05:15.000Z",
      "generator": {
        "date": "2026-09-13T07:02:34.794Z",
        "engine": {
          "name": "MSRC Generator",
          "version": "1.0"
        }
      },
      "id": "msrc_CVE-2026-80926",
      "initial_release_date": "2026-09-13T01:05:15.000Z",
      "revision_history": [
        {
          "date": "2026-09-13T01:05:15.000Z",
          "legacy_version": "1",
          "number": "1",
          "summary": "Information published."
        }
      ],
      "status": "final",
      "version": "1"
    }
  },
  "product_tree": {
    "branches": [
      {
        "branches": [
          {
            "branches": [
              {
                "category": "product_version",
                "name": "3.0",
                "product": {
                  "name": "Azure Linux 3.0",
                  "product_id": "17084"
                }
              }
            ],
            "category": "product_name",
            "name": "Azure Linux"
          },
          {
            "category": "product_name",
            "name": "azl3 kernel 0:6.6.150.1-1.azl3",
            "product": {
              "name": "azl3 kernel 0:6.6.150.1-1.azl3",
              "product_id": "1"
            }
          }
        ],
        "category": "vendor",
        "name": "Microsoft"
      }
    ],
    "relationships": [
      {
        "category": "default_component_of",
        "full_product_name": {
          "name": "azl3 kernel 0:6.6.150.1-1.azl3 as a component of Azure Linux 3.0",
          "product_id": "17084-1"
        },
        "product_reference": "1",
        "relates_to_product_reference": "17084"
      }
    ]
  },
  "vulnerabilities": [
    {
      "cve": "CVE-2026-80926",
      "notes": [
        {
          "category": "general",
          "text": "Linux",
          "title": "Assigning CNA"
        }
      ],
      "product_status": {
        "under_investigation": [
          "17084-1"
        ]
      },
      "references": [
        {
          "category": "self",
          "summary": "CVE-2026-80926 ksmbd: fix use-after-free in oplock break notification - VEX",
          "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-80926.json"
        }
      ],
      "title": "ksmbd: fix use-after-free in oplock break notification"
    }
  ]
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.

Action not permitted

CVE-2026-80926 (GCVE-0-2026-80926)

FKIE_CVE-2026-80926

GHSA-4R76-CQQC-V36J

MSRC_CVE-2026-80926

Tags

Sightings

Nomenclature