Vulnerability-Lookup

CVE-2026-89712 (GCVE-0-2026-89712)

Vulnerability from cvelistv5 – Published: 2026-09-11 19:46 – Updated: 2026-09-13 06:33

Title

NFSD: restart ssc_expire_umount walk after dropping nfsd_ssc_lock

Summary

In the Linux kernel, the following vulnerability has been resolved: NFSD: restart ssc_expire_umount walk after dropping nfsd_ssc_lock nfsd4_ssc_expire_umount() walks nn->nfsd_ssc_mount_list with list_for_each_entry_safe(ni, tmp, ...). For each expired entry it sets nsui_busy = true, drops nfsd_ssc_lock to run mntput() on the source vfsmount, then reacquires the lock to list_del + kfree the entry and continue iterating via the macro's saved tmp pointer. The nsui_busy flag protects the current ni from concurrent nfsd4_ssc_setup_dul() finders during the lock-drop window, but it does not pin tmp. Another nfsd RPC thread that fails its source- server mount and reaches nfsd4_ssc_cancel_dul() will, during that same window, take nfsd_ssc_lock, list_del + kfree its own ssc_umount item, and release the lock. If that item is the saved tmp of the expire walk, the next iteration dereferences a freed nfsd4_ssc_umount_item. Restart the walk from the head after the mntput() unlock window so no saved next pointer survives the lock-drop. The list is bounded by the number of active inter-server source mounts (typically small) and the expire delayed-work runs periodically rather than per-IO, so the restart is cheap.

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

4 references

URL	Tags
https://git.kernel.org/stable/c/77de363d9a1c8cd35…
https://git.kernel.org/stable/c/4ed8d2317aef21cc2…
https://git.kernel.org/stable/c/7377fa964b8aaf47c…
https://git.kernel.org/stable/c/036c1b182f4da6536…

Impacted products

2 products

Vendor	Product	Version	CPE status
Linux	Linux	Affected: f4e44b393389c77958f7c58bf4415032b4cda15b , < 77de363d9a1c8cd35f20482782c612cda085791a (git) Affected: f4e44b393389c77958f7c58bf4415032b4cda15b , < 4ed8d2317aef21cc2a9e5a55d6b59860b4b151a8 (git) Affected: f4e44b393389c77958f7c58bf4415032b4cda15b , < 7377fa964b8aaf47cb04e5efcc4c82d15e8c2ce9 (git) Affected: f4e44b393389c77958f7c58bf4415032b4cda15b , < 036c1b182f4da65363e79ec0ac276edc6b7296e5 (git) Affected: a4bc287943f5695209ff36bdc89f17b48d68fae7 (git) Affected: 5.10.220 , < 5.11 (semver)	guessed
Linux	Linux	Affected: 5.14 Unaffected: 0 , < 5.14 (semver) Unaffected: 6.12.109 , ≤ 6.12.* (semver) Unaffected: 6.18.50 , ≤ 6.18.* (semver) Unaffected: 7.2.4 , ≤ 7.2.* (semver) Unaffected: 7.3-rc1 , ≤ * (original_commit_for_fix)	guessed

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/nfsd/nfs4state.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "77de363d9a1c8cd35f20482782c612cda085791a",
              "status": "affected",
              "version": "f4e44b393389c77958f7c58bf4415032b4cda15b",
              "versionType": "git"
            },
            {
              "lessThan": "4ed8d2317aef21cc2a9e5a55d6b59860b4b151a8",
              "status": "affected",
              "version": "f4e44b393389c77958f7c58bf4415032b4cda15b",
              "versionType": "git"
            },
            {
              "lessThan": "7377fa964b8aaf47cb04e5efcc4c82d15e8c2ce9",
              "status": "affected",
              "version": "f4e44b393389c77958f7c58bf4415032b4cda15b",
              "versionType": "git"
            },
            {
              "lessThan": "036c1b182f4da65363e79ec0ac276edc6b7296e5",
              "status": "affected",
              "version": "f4e44b393389c77958f7c58bf4415032b4cda15b",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "a4bc287943f5695209ff36bdc89f17b48d68fae7",
              "versionType": "git"
            },
            {
              "lessThan": "5.11",
              "status": "affected",
              "version": "5.10.220",
              "versionType": "semver"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/nfsd/nfs4state.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.14"
            },
            {
              "lessThan": "5.14",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.109",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.50",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.4",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3-rc1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.109",
                  "versionStartIncluding": "5.14",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.50",
                  "versionStartIncluding": "5.14",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.4",
                  "versionStartIncluding": "5.14",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3-rc1",
                  "versionStartIncluding": "5.14",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionStartIncluding": "5.10.220",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nNFSD: restart ssc_expire_umount walk after dropping nfsd_ssc_lock\n\nnfsd4_ssc_expire_umount() walks nn-\u003enfsd_ssc_mount_list with\nlist_for_each_entry_safe(ni, tmp, ...).  For each expired entry it\nsets nsui_busy = true, drops nfsd_ssc_lock to run mntput() on the\nsource vfsmount, then reacquires the lock to list_del + kfree the\nentry and continue iterating via the macro\u0027s saved tmp pointer.\n\nThe nsui_busy flag protects the current ni from concurrent\nnfsd4_ssc_setup_dul() finders during the lock-drop window, but it\ndoes not pin tmp.  Another nfsd RPC thread that fails its source-\nserver mount and reaches nfsd4_ssc_cancel_dul() will, during that\nsame window, take nfsd_ssc_lock, list_del + kfree its own ssc_umount\nitem, and release the lock.  If that item is the saved tmp of the\nexpire walk, the next iteration dereferences a freed\nnfsd4_ssc_umount_item.\n\nRestart the walk from the head after the mntput() unlock window so\nno saved next pointer survives the lock-drop.  The list is bounded\nby the number of active inter-server source mounts (typically small)\nand the expire delayed-work runs periodically rather than per-IO,\nso the restart is cheap."
        }
      ],
      "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 - The UAF is between nfsd4_ssc_expire_umount() and nfsd4_ssc_cancel_dul(); cancel_dul runs from nfsd4_copy() on NFSv4.2 OP_COPY, reached by a COMPOUND over TCP/2049 to in-kernel nfsd. A remote client populates nfsd_ssc_mount_list and frees the saved iterator with no local access.\nAC:L - The attacker drives both race sides with concurrent async inter-server COPY requests: completed copies leave expired nfsd4_ssc_umount_item entries for the laundromat, while a COPY to another source IP fails vfs_kern_mount() into cancel_dul() during mntput(). An attacker-controlled source NFS server can stall unmount, so the window is attacker-created and retryable.\nPR:N - Under AUTH_SYS (default for typical NFS deployments) the server verifies no secret; EXCHANGE_ID, CREATE_SESSION, and OPEN succeed for any host allowed by the export, so no server-verified privileges are required to issue the COPY compounds that hit setup_dul/cancel_dul.\nUI:N - The attacker\u2019s own NFS client issues the COPY compounds and source-server traffic that create, expire, and cancel ssc_umount items; no administrator or other user action on the victim server is required.\nS:U - The use-after-free is of a kmalloc\u2019d nfsd4_ssc_umount_item in the nfsd host kernel; impact stays within the same kernel security authority and does not cross a VM, IOMMU, or sandbox boundary.\nC:H - After cancel_dul() kfree()s the saved tmp, the expire walk continues from a freed nfsd4_ssc_umount_item whose vfsmount, list links, and metadata the attacker can replace via slab reuse, giving a UAF read primitive over kernel heap.\nI:H - The expire path then writes nsui_busy, calls mntput() on attacker-controlled nsui_vfsmount, and runs list_del()/kfree() on poisoned pointers, yielding arbitrary-write and control-flow hijack primitives from the same UAF.\nA:H - Dereferencing the freed list node in nfsd4_ssc_expire_umount() oopses or panics the laundromat worker even without a full exploit, taking down the in-kernel NFS server."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-13T06:33:34.808Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/77de363d9a1c8cd35f20482782c612cda085791a"
        },
        {
          "url": "https://git.kernel.org/stable/c/4ed8d2317aef21cc2a9e5a55d6b59860b4b151a8"
        },
        {
          "url": "https://git.kernel.org/stable/c/7377fa964b8aaf47cb04e5efcc4c82d15e8c2ce9"
        },
        {
          "url": "https://git.kernel.org/stable/c/036c1b182f4da65363e79ec0ac276edc6b7296e5"
        }
      ],
      "title": "NFSD: restart ssc_expire_umount walk after dropping nfsd_ssc_lock",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89712",
    "datePublished": "2026-09-11T19:46:27.018Z",
    "dateReserved": "2026-09-11T19:38:34.751Z",
    "dateUpdated": "2026-09-13T06:33:34.808Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-89712",
      "date": "2026-09-13",
      "epss": "0.00626",
      "percentile": "0.48082"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-89712\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-09-11T20:19:58.620\",\"lastModified\":\"2026-09-13T07:17:36.853\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nNFSD: restart ssc_expire_umount walk after dropping nfsd_ssc_lock\\n\\nnfsd4_ssc_expire_umount() walks nn-\u003enfsd_ssc_mount_list with\\nlist_for_each_entry_safe(ni, tmp, ...).  For each expired entry it\\nsets nsui_busy = true, drops nfsd_ssc_lock to run mntput() on the\\nsource vfsmount, then reacquires the lock to list_del + kfree the\\nentry and continue iterating via the macro\u0027s saved tmp pointer.\\n\\nThe nsui_busy flag protects the current ni from concurrent\\nnfsd4_ssc_setup_dul() finders during the lock-drop window, but it\\ndoes not pin tmp.  Another nfsd RPC thread that fails its source-\\nserver mount and reaches nfsd4_ssc_cancel_dul() will, during that\\nsame window, take nfsd_ssc_lock, list_del + kfree its own ssc_umount\\nitem, and release the lock.  If that item is the saved tmp of the\\nexpire walk, the next iteration dereferences a freed\\nnfsd4_ssc_umount_item.\\n\\nRestart the walk from the head after the mntput() unlock window so\\nno saved next pointer survives the lock-drop.  The list is bounded\\nby the number of active inter-server source mounts (typically small)\\nand the expire delayed-work runs periodically rather than per-IO,\\nso the restart is cheap.\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"fs/nfsd/nfs4state.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"f4e44b393389c77958f7c58bf4415032b4cda15b\",\"lessThan\":\"77de363d9a1c8cd35f20482782c612cda085791a\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"f4e44b393389c77958f7c58bf4415032b4cda15b\",\"lessThan\":\"4ed8d2317aef21cc2a9e5a55d6b59860b4b151a8\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"f4e44b393389c77958f7c58bf4415032b4cda15b\",\"lessThan\":\"7377fa964b8aaf47cb04e5efcc4c82d15e8c2ce9\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"f4e44b393389c77958f7c58bf4415032b4cda15b\",\"lessThan\":\"036c1b182f4da65363e79ec0ac276edc6b7296e5\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"a4bc287943f5695209ff36bdc89f17b48d68fae7\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"5.10.220\",\"lessThan\":\"5.11\",\"versionType\":\"semver\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"fs/nfsd/nfs4state.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"5.14\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"5.14\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.12.109\",\"lessThanOrEqual\":\"6.12.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.18.50\",\"lessThanOrEqual\":\"6.18.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.2.4\",\"lessThanOrEqual\":\"7.2.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.3-rc1\",\"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/036c1b182f4da65363e79ec0ac276edc6b7296e5\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/4ed8d2317aef21cc2a9e5a55d6b59860b4b151a8\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/7377fa964b8aaf47cb04e5efcc4c82d15e8c2ce9\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/77de363d9a1c8cd35f20482782c612cda085791a\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}",
    "redhat_vex": {
      "aggregate_severity": "Important",
      "current_release_date": "2026-09-13T06:52:34+00:00",
      "cve": "CVE-2026-89712",
      "id": "CVE-2026-89712",
      "initial_release_date": "2026-09-11T19:46:27.018000+00:00",
      "product_status:known_affected": "2",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: Linux kernel NFSD: Denial of service via use-after-free",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89712.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-09-12T16:23:09Z",
      "cve": "CVE-2026-89712",
      "id": "CVE-2026-89712",
      "initial_release_date": "2026-09-12T16:23:09Z",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-89712",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-89712.json",
      "version": "2"
    }
  }
}

FKIE_CVE-2026-89712

Vulnerability from fkie_nvd - Published: 2026-09-11 20:19 - Updated: 2026-09-13 07:17

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/036c1b182f4da65363e79ec0ac276edc6b7296e5
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/4ed8d2317aef21cc2a9e5a55d6b59860b4b151a8
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/7377fa964b8aaf47cb04e5efcc4c82d15e8c2ce9
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/77de363d9a1c8cd35f20482782c612cda085791a

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/nfsd/nfs4state.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "77de363d9a1c8cd35f20482782c612cda085791a",
              "status": "affected",
              "version": "f4e44b393389c77958f7c58bf4415032b4cda15b",
              "versionType": "git"
            },
            {
              "lessThan": "4ed8d2317aef21cc2a9e5a55d6b59860b4b151a8",
              "status": "affected",
              "version": "f4e44b393389c77958f7c58bf4415032b4cda15b",
              "versionType": "git"
            },
            {
              "lessThan": "7377fa964b8aaf47cb04e5efcc4c82d15e8c2ce9",
              "status": "affected",
              "version": "f4e44b393389c77958f7c58bf4415032b4cda15b",
              "versionType": "git"
            },
            {
              "lessThan": "036c1b182f4da65363e79ec0ac276edc6b7296e5",
              "status": "affected",
              "version": "f4e44b393389c77958f7c58bf4415032b4cda15b",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "a4bc287943f5695209ff36bdc89f17b48d68fae7",
              "versionType": "git"
            },
            {
              "lessThan": "5.11",
              "status": "affected",
              "version": "5.10.220",
              "versionType": "semver"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/nfsd/nfs4state.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.14"
            },
            {
              "lessThan": "5.14",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.109",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.50",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.4",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3-rc1",
              "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\nNFSD: restart ssc_expire_umount walk after dropping nfsd_ssc_lock\n\nnfsd4_ssc_expire_umount() walks nn-\u003enfsd_ssc_mount_list with\nlist_for_each_entry_safe(ni, tmp, ...).  For each expired entry it\nsets nsui_busy = true, drops nfsd_ssc_lock to run mntput() on the\nsource vfsmount, then reacquires the lock to list_del + kfree the\nentry and continue iterating via the macro\u0027s saved tmp pointer.\n\nThe nsui_busy flag protects the current ni from concurrent\nnfsd4_ssc_setup_dul() finders during the lock-drop window, but it\ndoes not pin tmp.  Another nfsd RPC thread that fails its source-\nserver mount and reaches nfsd4_ssc_cancel_dul() will, during that\nsame window, take nfsd_ssc_lock, list_del + kfree its own ssc_umount\nitem, and release the lock.  If that item is the saved tmp of the\nexpire walk, the next iteration dereferences a freed\nnfsd4_ssc_umount_item.\n\nRestart the walk from the head after the mntput() unlock window so\nno saved next pointer survives the lock-drop.  The list is bounded\nby the number of active inter-server source mounts (typically small)\nand the expire delayed-work runs periodically rather than per-IO,\nso the restart is cheap."
    }
  ],
  "id": "CVE-2026-89712",
  "lastModified": "2026-09-13T07:17:36.853",
  "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": "2026-09-11T20:19:58.620",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/036c1b182f4da65363e79ec0ac276edc6b7296e5"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/4ed8d2317aef21cc2a9e5a55d6b59860b4b151a8"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/7377fa964b8aaf47cb04e5efcc4c82d15e8c2ce9"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/77de363d9a1c8cd35f20482782c612cda085791a"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}

GHSA-CFXC-M2R2-5GRW

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:

NFSD: restart ssc_expire_umount walk after dropping nfsd_ssc_lock

nfsd4_ssc_expire_umount() walks nn->nfsd_ssc_mount_list with list_for_each_entry_safe(ni, tmp, ...). For each expired entry it sets nsui_busy = true, drops nfsd_ssc_lock to run mntput() on the source vfsmount, then reacquires the lock to list_del + kfree the entry and continue iterating via the macro's saved tmp pointer.

The nsui_busy flag protects the current ni from concurrent nfsd4_ssc_setup_dul() finders during the lock-drop window, but it does not pin tmp. Another nfsd RPC thread that fails its source- server mount and reaches nfsd4_ssc_cancel_dul() will, during that same window, take nfsd_ssc_lock, list_del + kfree its own ssc_umount item, and release the lock. If that item is the saved tmp of the expire walk, the next iteration dereferences a freed nfsd4_ssc_umount_item.

Restart the walk from the head after the mntput() unlock window so no saved next pointer survives the lock-drop. The list is bounded by the number of active inter-server source mounts (typically small) and the expire delayed-work runs periodically rather than per-IO, so the restart is cheap.

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

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{
  "affected": [],
  "aliases": [
    "CVE-2026-89712"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-09-11T20:19:58Z",
    "severity": "CRITICAL"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nNFSD: restart ssc_expire_umount walk after dropping nfsd_ssc_lock\n\nnfsd4_ssc_expire_umount() walks nn-\u003enfsd_ssc_mount_list with\nlist_for_each_entry_safe(ni, tmp, ...).  For each expired entry it\nsets nsui_busy = true, drops nfsd_ssc_lock to run mntput() on the\nsource vfsmount, then reacquires the lock to list_del + kfree the\nentry and continue iterating via the macro\u0027s saved tmp pointer.\n\nThe nsui_busy flag protects the current ni from concurrent\nnfsd4_ssc_setup_dul() finders during the lock-drop window, but it\ndoes not pin tmp.  Another nfsd RPC thread that fails its source-\nserver mount and reaches nfsd4_ssc_cancel_dul() will, during that\nsame window, take nfsd_ssc_lock, list_del + kfree its own ssc_umount\nitem, and release the lock.  If that item is the saved tmp of the\nexpire walk, the next iteration dereferences a freed\nnfsd4_ssc_umount_item.\n\nRestart the walk from the head after the mntput() unlock window so\nno saved next pointer survives the lock-drop.  The list is bounded\nby the number of active inter-server source mounts (typically small)\nand the expire delayed-work runs periodically rather than per-IO,\nso the restart is cheap.",
  "id": "GHSA-cfxc-m2r2-5grw",
  "modified": "2026-09-13T09:32:28Z",
  "published": "2026-09-11T21:31:37Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-89712"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/036c1b182f4da65363e79ec0ac276edc6b7296e5"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/4ed8d2317aef21cc2a9e5a55d6b59860b4b151a8"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/7377fa964b8aaf47cb04e5efcc4c82d15e8c2ce9"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/77de363d9a1c8cd35f20482782c612cda085791a"
    }
  ],
  "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"
    }
  ]
}

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-2026-89712 (GCVE-0-2026-89712)

FKIE_CVE-2026-89712

GHSA-CFXC-M2R2-5GRW

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Nomenclature