Vulnerability-Lookup

FKIE_CVE-2026-89660

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

In the Linux kernel, the following vulnerability has been resolved: NFSD: Prevent client use-after-free during admin state revocation A stateid holds only a bare pointer to its nfs4_client; a stateid reference does not pin it. The client survives only because __destroy_client() drains its stateids before free_client() runs. nfsd4_revoke_states() drops nn->client_lock across revoke_one_stid(), which dereferences the client to revoke a stateid and read clp->cl_minorversion. A teardown racing the dropped lock can free the client first. Pinning cl_rpc_users under client_lock blocks the DESTROY_CLIENTID and EXCHANGE_ID teardown, which refuses while cl_rpc_users is non-zero. force_expire_client() ignores it: once its wait for cl_rpc_users to reach zero has passed, a later pin goes unnoticed. Under client_lock, skip a client whose cl_time is already zero -- force_expire_client() clears it there before waiting -- otherwise pin cl_rpc_users before dropping the lock. The walk then either sees the expiry and skips, or pins in time for that wait to cover the revoke.

References

	URL	Tags
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/549bd9868e9d77b07ea94870940d64342829c6ad
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/bf1f948691523282cc4905bc6cd325e0c0b49e6a
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/e270e5a0778e5bff852c8862ce9576ce70359393

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": "549bd9868e9d77b07ea94870940d64342829c6ad",
              "status": "affected",
              "version": "1c13bf9f2e3cd5a59ef988c6c5a49fe0f02bcdfc",
              "versionType": "git"
            },
            {
              "lessThan": "bf1f948691523282cc4905bc6cd325e0c0b49e6a",
              "status": "affected",
              "version": "1c13bf9f2e3cd5a59ef988c6c5a49fe0f02bcdfc",
              "versionType": "git"
            },
            {
              "lessThan": "e270e5a0778e5bff852c8862ce9576ce70359393",
              "status": "affected",
              "version": "1c13bf9f2e3cd5a59ef988c6c5a49fe0f02bcdfc",
              "versionType": "git"
            }
          ]
        },
        {
          "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": "6.9"
            },
            {
              "lessThan": "6.9",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.51",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.4",
              "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: Prevent client use-after-free during admin state revocation\n\nA stateid holds only a bare pointer to its nfs4_client; a stateid\nreference does not pin it.  The client survives only because\n__destroy_client() drains its stateids before free_client() runs.\n\nnfsd4_revoke_states() drops nn-\u003eclient_lock across revoke_one_stid(),\nwhich dereferences the client to revoke a stateid and read\nclp-\u003ecl_minorversion.  A teardown racing the dropped lock can free\nthe client first.\n\nPinning cl_rpc_users under client_lock blocks the DESTROY_CLIENTID and\nEXCHANGE_ID teardown, which refuses while cl_rpc_users is non-zero.\nforce_expire_client() ignores it: once its wait for cl_rpc_users to\nreach zero has passed, a later pin goes unnoticed.\n\nUnder client_lock, skip a client whose cl_time is already zero --\nforce_expire_client() clears it there before waiting -- otherwise pin\ncl_rpc_users before dropping the lock.  The walk then either sees the\nexpiry and skips, or pins in time for that wait to cover the revoke."
    }
  ],
  "id": "CVE-2026-89660",
  "lastModified": "2026-09-13T07:17:31.647",
  "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": "2026-09-11T20:19:52.300",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/549bd9868e9d77b07ea94870940d64342829c6ad"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/bf1f948691523282cc4905bc6cd325e0c0b49e6a"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/e270e5a0778e5bff852c8862ce9576ce70359393"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}

CVE-2026-89660 (GCVE-0-2026-89660)

Vulnerability from cvelistv5 – Published: 2026-09-11 19:45 – Updated: 2026-09-13 06:32

Title

NFSD: Prevent client use-after-free during admin state revocation

Summary

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/549bd9868e9d77b07…
https://git.kernel.org/stable/c/bf1f948691523282c…
https://git.kernel.org/stable/c/e270e5a0778e5bff8…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 1c13bf9f2e3cd5a59ef988c6c5a49fe0f02bcdfc , < 549bd9868e9d77b07ea94870940d64342829c6ad (git) Affected: 1c13bf9f2e3cd5a59ef988c6c5a49fe0f02bcdfc , < bf1f948691523282cc4905bc6cd325e0c0b49e6a (git) Affected: 1c13bf9f2e3cd5a59ef988c6c5a49fe0f02bcdfc , < e270e5a0778e5bff852c8862ce9576ce70359393 (git)
Linux	Linux	Affected: 6.9 Unaffected: 0 , < 6.9 (semver) Unaffected: 6.18.51 , ≤ 6.18.* (semver) Unaffected: 7.2.4 , ≤ 7.2.* (semver) Unaffected: 7.3-rc1 , ≤ * (original_commit_for_fix)

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": "549bd9868e9d77b07ea94870940d64342829c6ad",
              "status": "affected",
              "version": "1c13bf9f2e3cd5a59ef988c6c5a49fe0f02bcdfc",
              "versionType": "git"
            },
            {
              "lessThan": "bf1f948691523282cc4905bc6cd325e0c0b49e6a",
              "status": "affected",
              "version": "1c13bf9f2e3cd5a59ef988c6c5a49fe0f02bcdfc",
              "versionType": "git"
            },
            {
              "lessThan": "e270e5a0778e5bff852c8862ce9576ce70359393",
              "status": "affected",
              "version": "1c13bf9f2e3cd5a59ef988c6c5a49fe0f02bcdfc",
              "versionType": "git"
            }
          ]
        },
        {
          "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": "6.9"
            },
            {
              "lessThan": "6.9",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.51",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.4",
              "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": "6.18.51",
                  "versionStartIncluding": "6.9",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.4",
                  "versionStartIncluding": "6.9",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3-rc1",
                  "versionStartIncluding": "6.9",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nNFSD: Prevent client use-after-free during admin state revocation\n\nA stateid holds only a bare pointer to its nfs4_client; a stateid\nreference does not pin it.  The client survives only because\n__destroy_client() drains its stateids before free_client() runs.\n\nnfsd4_revoke_states() drops nn-\u003eclient_lock across revoke_one_stid(),\nwhich dereferences the client to revoke a stateid and read\nclp-\u003ecl_minorversion.  A teardown racing the dropped lock can free\nthe client first.\n\nPinning cl_rpc_users under client_lock blocks the DESTROY_CLIENTID and\nEXCHANGE_ID teardown, which refuses while cl_rpc_users is non-zero.\nforce_expire_client() ignores it: once its wait for cl_rpc_users to\nreach zero has passed, a later pin goes unnoticed.\n\nUnder client_lock, skip a client whose cl_time is already zero --\nforce_expire_client() clears it there before waiting -- otherwise pin\ncl_rpc_users before dropping the lock.  The walk then either sees the\nexpiry and skips, or pins in time for that wait to cover the revoke."
        }
      ],
      "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 in nfsd nfsd4_revoke_states(). A remote NFSv4 peer reaches the racing expire_client() over TCP/2049 via EXCHANGE_ID/CREATE_SESSION, SETCLIENTID_CONFIRM, or DESTROY_CLIENTID (ALLOWED_WITHOUT_FH), which free nfs4_client while the revoke walk still dereferences it.\nAC:L - The attacker controls the teardown side: they hold many stateids so the revoke walk drops client_lock once per stid, and concurrently retry EXCHANGE_ID/CREATE_SESSION or SETCLIENTID_CONFIRM so mark_client_expired_locked() succeeds while cl_rpc_users is unpinned.\nPR:N - EXCHANGE_ID, CREATE_SESSION, SETCLIENTID, SETCLIENTID_CONFIRM, and DESTROY_CLIENTID are ALLOWED_WITHOUT_FH with no export check. Typical AUTH_SYS/AUTH_NULL nfsd deployments do not verify RPC credentials, so any host that can reach TCP/2049 can establish state and trigger expire.\nUI:N - The attacker drives the NFS compounds that create state and expire the client. Administrative unlock_filesystem/unexport is a server operational condition (unexport or response to a misbehaving client), not a required victim user action.\nS:U - The freed object is struct nfs4_client in the NFS server kernel. Impact remains in that kernel security authority; there is no VM, IOMMU, or sandbox boundary crossing.\nC:H - revoke_one_stid() and the subsequent clp-\u003ecl_minorversion read dereference nfs4_client after free_client() kmem_cache_free\u0027s the mergeable client_slab object (KMEM_CACHE flags 0). Reclaim via EXCHANGE_ID discloses kernel memory; a UAF is C:H.\nI:H - revoke_one_stid() takes cl_lock and nfs4_put_stid() does refcount_dec_and_lock/idr_remove on the freed client\u0027s cl_lock/cl_stateids, concurrent with __destroy_client(), a slab UAF write primitive for heap corruption and control-flow hijacking.\nA:H - Use-after-free of nfs4_client in the nfsd revoke path oopses or panics the NFS server even without full exploitation, fully denying service of the host."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-13T06:32:43.237Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/549bd9868e9d77b07ea94870940d64342829c6ad"
        },
        {
          "url": "https://git.kernel.org/stable/c/bf1f948691523282cc4905bc6cd325e0c0b49e6a"
        },
        {
          "url": "https://git.kernel.org/stable/c/e270e5a0778e5bff852c8862ce9576ce70359393"
        }
      ],
      "title": "NFSD: Prevent client use-after-free during admin state revocation",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89660",
    "datePublished": "2026-09-11T19:45:48.341Z",
    "dateReserved": "2026-09-11T19:38:34.744Z",
    "dateUpdated": "2026-09-13T06:32:43.237Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

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.
Browse all ATT&CK techniques and the vulnerabilities related to each.

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