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CVE-2026-89703 (GCVE-0-2026-89703)

Vulnerability from cvelistv5 – Published: 2026-09-11 19:46 – Updated: 2026-09-13 06:33
VLAI
Title
nfsd: set SC_STATUS_FREED in nfsd4_drop_revoked_stid for delegations
Summary
In the Linux kernel, the following vulnerability has been resolved: nfsd: set SC_STATUS_FREED in nfsd4_drop_revoked_stid for delegations nfsd4_drop_revoked_stid() handles FREE_STATEID for admin-revoked delegations but does not set SC_STATUS_FREED before releasing cl_lock. revoke_delegation() uses this flag to detect whether FREE_STATEID has already processed the delegation -- without it, the freed delegation is added to cl_revoked via list_add(), producing a use-after-free when cl_revoked is later traversed in __destroy_client(). The SC_STATUS_REVOKED path in nfsd4_free_stateid() (line 7983) already sets SC_STATUS_FREED correctly. Apply the same pattern to the SC_STATUS_ADMIN_REVOKED path in nfsd4_drop_revoked_stid().
Severity
9.8 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 8dd91e8d31febf4d9cca3ae1bb4771d33ae7ee5a , < d832a0587528853d45481d1faf75d4b5d062adaf (git)
Affected: 8dd91e8d31febf4d9cca3ae1bb4771d33ae7ee5a , < 1e4795766719ffd74b8cf0f2fde4a1350f8326bf (git)
Affected: 8dd91e8d31febf4d9cca3ae1bb4771d33ae7ee5a , < a6d89032e5c6620d5bb44582a72555ce07bf1c2e (git)
Affected: 8dd91e8d31febf4d9cca3ae1bb4771d33ae7ee5a , < 650d370cfbc66a96dd14d517bd704689b5bda4e5 (git)
Affected: 967faa26f313a62e7bebc55d5b8122eaee43b929 (git)
Affected: 6.11.6 , < 6.12 (semver)
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Linux Linux Affected: 6.12
Unaffected: 0 , < 6.12 (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)
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          "product": "Linux",
          "programFiles": [
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              "version": "7.3-rc1",
              "versionType": "original_commit_for_fix"
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                  "versionStartIncluding": "6.12",
                  "vulnerable": true
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              "negate": false,
              "operator": "OR"
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: set SC_STATUS_FREED in nfsd4_drop_revoked_stid for delegations\n\nnfsd4_drop_revoked_stid() handles FREE_STATEID for admin-revoked\ndelegations but does not set SC_STATUS_FREED before releasing cl_lock.\nrevoke_delegation() uses this flag to detect whether FREE_STATEID has\nalready processed the delegation -- without it, the freed delegation is\nadded to cl_revoked via list_add(), producing a use-after-free when\ncl_revoked is later traversed in __destroy_client().\n\nThe SC_STATUS_REVOKED path in nfsd4_free_stateid() (line 7983) already\nsets SC_STATUS_FREED correctly. Apply the same pattern to the\nSC_STATUS_ADMIN_REVOKED path in nfsd4_drop_revoked_stid()."
        }
      ],
      "metrics": [
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            "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"
          },
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              "value": "AV:N - The UAF is in nfsd nfsd4_drop_revoked_stid()/revoke_delegation() in fs/nfsd/nfs4state.c. A remote NFSv4 peer reaches it over TCP/2049 via svc_process to nfsd_dispatch to nfsd4_proc_compound: SEQUENCE then FREE_STATEID (ALLOWED_WITHOUT_FH), or a v4.0 op that hits nfsd40_drop_revoked_stid on an admin-revoked delegation.\nAC:L - The attacker holds a delegation and retries FREE_STATEID (or v4.0 use of that stateid) while nfsd4_revoke_states() unhashes with ADMIN_REVOKED and revoke_delegation() runs, then DESTROY_CLIENTID/expire so __destroy_client() walks cl_revoked. They control the NFS side of the race; unexport is a routine nfsd operational condition, not an uninfluenced layout.\nPR:N - Typical nfsd deployments use AUTH_SYS/AUTH_NULL with no cryptographic RPC authentication. Any host allowed by the export can EXCHANGE_ID/CREATE_SESSION or SETCLIENTID, OPEN to receive a delegation, and issue FREE_STATEID; no local Linux account or capability on the NFS server is required.\nUI:N - The attacker sends the NFSv4 compounds that obtain the delegation, FREE_STATEID, and client teardown. Administrative unlock_filesystem/unexport is a server operational condition (exportfs -u or volume detach), not a required victim user action such as mounting or opening a file.\nS:U - The use-after-free corrupts a kmalloc\u0027d nfs4_delegation (deleg_slab) in the NFS server kernel. Impact stays in that host kernel security authority and does not cross a VM, IOMMU, or sandbox boundary.\nC:H - Without SC_STATUS_FREED, revoke_delegation() list_add()s a kmem_cache_free\u0027d nfs4_delegation onto cl_revoked (KMEM_CACHE flags 0, not SLAB_TYPESAFE_BY_RCU). __destroy_client() then walks that freed object; slab reuse yields an arbitrary kernel-read primitive. Per guidance a UAF is C:H.\nI:H - list_add on the freed dl_recall_lru and later list_del_init/nfs4_put_stid in __destroy_client() write through reclaimed deleg_slab, including sc_free. That is a heap-spray write and control-flow hijack primitive. Per guidance a UAF is I:H.\nA:H - Use-after-free of nfs4_delegation when __destroy_client() traverses cl_revoked oopses or panics the nfsd thread even without full exploitation, fully denying service of the NFS server host."
            }
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        "dateUpdated": "2026-09-13T06:33:24.763Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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        },
        {
          "url": "https://git.kernel.org/stable/c/650d370cfbc66a96dd14d517bd704689b5bda4e5"
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      ],
      "title": "nfsd: set SC_STATUS_FREED in nfsd4_drop_revoked_stid for delegations",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89703",
    "datePublished": "2026-09-11T19:46:20.280Z",
    "dateReserved": "2026-09-11T19:38:34.750Z",
    "dateUpdated": "2026-09-13T06:33:24.763Z",
    "state": "PUBLISHED"
  },
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            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: set SC_STATUS_FREED in nfsd4_drop_revoked_stid for delegations\n\nnfsd4_drop_revoked_stid() handles FREE_STATEID for admin-revoked\ndelegations but does not set SC_STATUS_FREED before releasing cl_lock.\nrevoke_delegation() uses this flag to detect whether FREE_STATEID has\nalready processed the delegation -- without it, the freed delegation is\nadded to cl_revoked via list_add(), producing a use-after-free when\ncl_revoked is later traversed in __destroy_client().\n\nThe SC_STATUS_REVOKED path in nfsd4_free_stateid() (line 7983) already\nsets SC_STATUS_FREED correctly. Apply the same pattern to the\nSC_STATUS_ADMIN_REVOKED path in nfsd4_drop_revoked_stid()."
          }
        ],
        "id": "CVE-2026-89703",
        "lastModified": "2026-09-13T07:17:35.860",
        "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"
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              "impactScore": 5.9,
              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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        "published": "2026-09-11T20:19:57.537",
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        "vulnStatus": "Received"
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    },
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-09-15T15:02:34+00:00",
      "cve": "CVE-2026-89703",
      "id": "CVE-2026-89703",
      "initial_release_date": "2026-09-11T00:00:00+00:00",
      "product_status:known_affected": "199",
      "product_status:known_not_affected": "77",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: nfsd: set SC_STATUS_FREED in nfsd4_drop_revoked_stid for delegations",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89703.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "important",
      "current_release_date": "2026-09-15T23:59:50Z",
      "cve": "CVE-2026-89703",
      "id": "CVE-2026-89703",
      "initial_release_date": "2026-09-12T16:23:19Z",
      "product_status:known_affected": "85",
      "product_status:known_not_affected": "268",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-89703",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-89703.json",
      "version": "4"
    }
  }
}



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