Vulnerability-Lookup

FKIE_CVE-2026-89659

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 delegation revoke A delegation stateid holds only a bare pointer to its owning nfs4_client and does not keep it alive. The client survives its stateids only because __destroy_client() drains cl_delegations and cl_revoked before free_client() runs. nfs4_laundromat() breaks that invariant: it unhashes an expired delegation from cl_delegations, drops deleg_lock, then revoke_delegation() relinks it onto cl_revoked under cl_lock. In that window the delegation is on neither list, so client_has_state() can report no remaining state. Every teardown path first requires cl_rpc_users to be zero, but the laundromat holds no such reference. A client whose recalled delegation has just timed out can therefore reach free_client() while revoke_delegation() is still about to dereference cl_lock, a use-after-free. Pin the client with cl_rpc_users across the revoke so teardown blocks until it completes, then reap the delegation from cl_revoked. A client already expiring reaps its own, so skip it and leave the delegation on del_recall_lru.

References

	URL	Tags
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/2a9d637c2a8fd8ac29ad9b29f28d122ef75c1a56
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/3c0a53ee0b442348d8d2286d6960d3f07bb3a3d3
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/4683ca76b3b7e5808338491c6eb3c20e6b4894d5

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/nfsd/netns.h",
            "fs/nfsd/nfs4state.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "3c0a53ee0b442348d8d2286d6960d3f07bb3a3d3",
              "status": "affected",
              "version": "3bd64a5ba1719c2bb6cba4493dfd3e23a7653e54",
              "versionType": "git"
            },
            {
              "lessThan": "2a9d637c2a8fd8ac29ad9b29f28d122ef75c1a56",
              "status": "affected",
              "version": "3bd64a5ba1719c2bb6cba4493dfd3e23a7653e54",
              "versionType": "git"
            },
            {
              "lessThan": "4683ca76b3b7e5808338491c6eb3c20e6b4894d5",
              "status": "affected",
              "version": "3bd64a5ba1719c2bb6cba4493dfd3e23a7653e54",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/nfsd/netns.h",
            "fs/nfsd/nfs4state.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "3.10"
            },
            {
              "lessThan": "3.10",
              "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 delegation revoke\n\nA delegation stateid holds only a bare pointer to its owning\nnfs4_client and does not keep it alive.  The client survives its\nstateids only because __destroy_client() drains cl_delegations and\ncl_revoked before free_client() runs.\n\nnfs4_laundromat() breaks that invariant: it unhashes an\nexpired delegation from cl_delegations, drops deleg_lock, then\nrevoke_delegation() relinks it onto cl_revoked under cl_lock.  In that\nwindow the delegation is on neither list, so client_has_state() can\nreport no remaining state.\n\nEvery teardown path first requires cl_rpc_users to be zero, but\nthe laundromat holds no such reference.  A client whose recalled\ndelegation has just timed out can therefore reach free_client()\nwhile revoke_delegation() is still about to dereference cl_lock,\na use-after-free.\n\nPin the client with cl_rpc_users across the revoke so teardown blocks\nuntil it completes, then reap the delegation from cl_revoked.  A client\nalready expiring reaps its own, so skip it and leave the delegation on\ndel_recall_lru."
    }
  ],
  "id": "CVE-2026-89659",
  "lastModified": "2026-09-13T07:17:31.523",
  "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": "2026-09-11T20:19:52.180",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/2a9d637c2a8fd8ac29ad9b29f28d122ef75c1a56"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/3c0a53ee0b442348d8d2286d6960d3f07bb3a3d3"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/4683ca76b3b7e5808338491c6eb3c20e6b4894d5"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}

CVE-2026-89659 (GCVE-0-2026-89659)

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

Title

NFSD: Prevent client use-after-free during delegation revoke

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/3c0a53ee0b442348d…
https://git.kernel.org/stable/c/2a9d637c2a8fd8ac2…
https://git.kernel.org/stable/c/4683ca76b3b7e5808…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 3bd64a5ba1719c2bb6cba4493dfd3e23a7653e54 , < 3c0a53ee0b442348d8d2286d6960d3f07bb3a3d3 (git) Affected: 3bd64a5ba1719c2bb6cba4493dfd3e23a7653e54 , < 2a9d637c2a8fd8ac29ad9b29f28d122ef75c1a56 (git) Affected: 3bd64a5ba1719c2bb6cba4493dfd3e23a7653e54 , < 4683ca76b3b7e5808338491c6eb3c20e6b4894d5 (git)
Linux	Linux	Affected: 3.10 Unaffected: 0 , < 3.10 (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/netns.h",
            "fs/nfsd/nfs4state.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "3c0a53ee0b442348d8d2286d6960d3f07bb3a3d3",
              "status": "affected",
              "version": "3bd64a5ba1719c2bb6cba4493dfd3e23a7653e54",
              "versionType": "git"
            },
            {
              "lessThan": "2a9d637c2a8fd8ac29ad9b29f28d122ef75c1a56",
              "status": "affected",
              "version": "3bd64a5ba1719c2bb6cba4493dfd3e23a7653e54",
              "versionType": "git"
            },
            {
              "lessThan": "4683ca76b3b7e5808338491c6eb3c20e6b4894d5",
              "status": "affected",
              "version": "3bd64a5ba1719c2bb6cba4493dfd3e23a7653e54",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/nfsd/netns.h",
            "fs/nfsd/nfs4state.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "3.10"
            },
            {
              "lessThan": "3.10",
              "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": "3.10",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.4",
                  "versionStartIncluding": "3.10",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3-rc1",
                  "versionStartIncluding": "3.10",
                  "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 delegation revoke\n\nA delegation stateid holds only a bare pointer to its owning\nnfs4_client and does not keep it alive.  The client survives its\nstateids only because __destroy_client() drains cl_delegations and\ncl_revoked before free_client() runs.\n\nnfs4_laundromat() breaks that invariant: it unhashes an\nexpired delegation from cl_delegations, drops deleg_lock, then\nrevoke_delegation() relinks it onto cl_revoked under cl_lock.  In that\nwindow the delegation is on neither list, so client_has_state() can\nreport no remaining state.\n\nEvery teardown path first requires cl_rpc_users to be zero, but\nthe laundromat holds no such reference.  A client whose recalled\ndelegation has just timed out can therefore reach free_client()\nwhile revoke_delegation() is still about to dereference cl_lock,\na use-after-free.\n\nPin the client with cl_rpc_users across the revoke so teardown blocks\nuntil it completes, then reap the delegation from cl_revoked.  A client\nalready expiring reaps its own, so skip it and leave the delegation on\ndel_recall_lru."
        }
      ],
      "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 bug is in nfsd nfs4_laundromat()/revoke_delegation() in fs/nfsd/nfs4state.c. A remote NFSv4 client reaches it over TCP/2049 by OPEN to obtain a delegation, a conflicting OPEN to force CB_RECALL, then DESTROY_CLIENTID or CREATE_SESSION replacement while the laundromat revokes.\nAC:L - The attacker controls both sides: it creates the recalled delegation, learns FATTR4_LEASE_TIME, and issues DESTROY_CLIENTID or same-name CREATE_SESSION/SETCLIENTID_CONFIRM while laundromat unhashes. Many recalled delegations widen the unhash-to-revoke window, and the sequence is retryable.\nPR:N - Default AUTH_SYS nfsd exports do no cryptographic authentication; any host allowed by the export ACL can EXCHANGE_ID/SETCLIENTID, OPEN to get a delegation, and DESTROY_CLIENTID. No local account or capability on the NFS server is required.\nUI:N - The attacking NFS client performs the full sequence itself (delegation, recall, teardown). No local user or administrator action on the NFS server is required at attack time.\nS:U - The use-after-free corrupts the nfs4_client object in the host kernel\u0027s nfsd state tables. Impact stays in that kernel security authority and does not cross a VM, IOMMU, or sandbox boundary.\nC:H - revoke_delegation() and nfs4_put_stid() dereference sc_client (cl_lock, cl_revoked, cl_stateids) after free_client() kmem_cache_free\u0027s the mergeable client_slab object (KMEM_CACHE flags 0), a UAF the attacker can reallocate via EXCHANGE_ID to disclose kernel memory.\nI:H - The UAF writes include spin_lock/unlock of freed cl_lock, list_add onto cl_revoked, and refcount_dec_and_lock in nfs4_put_stid on a reclaimable nfs4_client, enabling heap corruption and control-flow hijack.\nA:H - Use-after-free of nfs4_client in an nfsd/laundromat thread oopses or panics the NFS server even without full exploitation, and the attacker can repeat the RPC sequence to deny service."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-13T06:32:42.114Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/3c0a53ee0b442348d8d2286d6960d3f07bb3a3d3"
        },
        {
          "url": "https://git.kernel.org/stable/c/2a9d637c2a8fd8ac29ad9b29f28d122ef75c1a56"
        },
        {
          "url": "https://git.kernel.org/stable/c/4683ca76b3b7e5808338491c6eb3c20e6b4894d5"
        }
      ],
      "title": "NFSD: Prevent client use-after-free during delegation revoke",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89659",
    "datePublished": "2026-09-11T19:45:47.587Z",
    "dateReserved": "2026-09-11T19:38:34.744Z",
    "dateUpdated": "2026-09-13T06:32:42.114Z",
    "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.

Related by attack behaviour

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