CVE-2026-89658 (GCVE-0-2026-89658)
Vulnerability from cvelistv5
Published
2026-09-11 19:45
Modified
2026-10-19 08:50
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 NFSv4.0 revoked-state cleanup nfs40_clean_admin_revoked() takes a stateid reference under clp->cl_lock, drops nn->client_lock, and calls nfsd4_drop_revoked_stid(), which dereferences the stateid's client through s->sc_client->cl_lock. The stateid reference does not pin the client, so a teardown racing the dropped lock can free the client while nfsd4_drop_revoked_stid() is still using it. This cleanup runs from the laundromat, so a periodic sweep can race force_expire_client() driven by a write to the clients/<id>/ctl file. Skip a client that is already expiring and otherwise pin it with cl_rpc_users under client_lock before dropping the lock, matching nfsd4_revoke_states().
References
Impacted products
Vendor Product Version
Linux Linux Version: d688d8585e6bea5e4e37f7497feea93b6b0a469c
Version: d688d8585e6bea5e4e37f7497feea93b6b0a469c
Version: d688d8585e6bea5e4e37f7497feea93b6b0a469c
Version: d688d8585e6bea5e4e37f7497feea93b6b0a469c
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{
  "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",
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              "status": "affected",
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              "versionType": "git"
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              "status": "affected",
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              "versionType": "git"
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              "lessThan": "81cf7f1413862f87b078920c838460a6a88aa030",
              "status": "affected",
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              "versionType": "git"
            },
            {
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              "status": "affected",
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              "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": "6.12.*",
              "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",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.109",
                  "versionStartIncluding": "6.9",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.50",
                  "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",
                  "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 NFSv4.0 revoked-state cleanup\n\nnfs40_clean_admin_revoked() takes a stateid reference under\nclp-\u003ecl_lock, drops nn-\u003eclient_lock, and calls\nnfsd4_drop_revoked_stid(), which dereferences the stateid\u0027s client\nthrough s-\u003esc_client-\u003ecl_lock.  The stateid reference does not pin the\nclient, so a teardown racing the dropped lock can free the client\nwhile nfsd4_drop_revoked_stid() is still using it.\n\nThis cleanup runs from the laundromat, so a periodic sweep can race\nforce_expire_client() driven by a write to the clients/\u003cid\u003e/ctl file.\n\nSkip a client that is already expiring and otherwise pin it with\ncl_rpc_users under client_lock before dropping the lock, matching\nnfsd4_revoke_states()."
        }
      ],
      "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 NFSv4.0 revoked-state cleanup (nfs40_clean_admin_revoked). A remote peer reaches it over TCP/2049 via nfsd_dispatch to nfsd4_proc_compound: SETCLIENTID/SETCLIENTID_CONFIRM (ALLOWED_WITHOUT_FH) call expire_client() while the laundromat still uses the client.\nAC:L - The attacker controls the expire side by retrying SETCLIENTID_CONFIRM around the known lease interval, or by inducing the documented clients/\u003cid\u003e/ctl expire of a misbehaving client. Cleanup drops client_lock without pinning cl_rpc_users, so mark_client_expired_locked succeeds; this is not a race outside attacker influence.\nPR:N - OP_SETCLIENTID and OP_SETCLIENTID_CONFIRM are ALLOWED_WITHOUT_FH/ALLOWED_ON_ABSENT_FS with no export check. Typical nfsd AUTH_SYS/AUTH_NULL deployments never verify RPC credentials, so any host that can reach TCP/2049 can create NFSv4.0 state and trigger the expire.\nUI:N - The attacker drives the NFS compounds that establish state and expire the client. Administrative revoke or ctl expire 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 - nfsd4_drop_revoked_stid() and nfs4_put_stid() dereference s-\u003esc_client after expire_client() frees the nfs4_client. Reclaim of that slab lets an attacker groom contents and disclose kernel memory. Per kernel guidance a UAF is C:H.\nI:H - nfs4_put_stid() lock-and-idr_remove on the freed client\u0027s cl_lock/cl_stateids, concurrent with __destroy_client() list walks, is a slab UAF write primitive usable for heap corruption and control-flow hijacking. Per kernel guidance a UAF is I:H.\nA:H - Use of the freed nfs4_client spinlock, IDR, and lists oopses or panics the nfsd host, fully denying service of the NFS server."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T08:50:29.852Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/0ae0d2b5c5a1b39c0b3c15d96b32a5b0c583d519"
        },
        {
          "url": "https://git.kernel.org/stable/c/b413ec5b23e3445dc9c4f273116078e2d4747626"
        },
        {
          "url": "https://git.kernel.org/stable/c/81cf7f1413862f87b078920c838460a6a88aa030"
        },
        {
          "url": "https://git.kernel.org/stable/c/7b4f8a1586c42d3afc3c0ac779af2db7ab1a5c55"
        }
      ],
      "title": "NFSD: Prevent client use-after-free during NFSv4.0 revoked-state cleanup",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89658",
    "datePublished": "2026-09-11T19:45:46.857Z",
    "dateReserved": "2026-09-11T19:38:34.743Z",
    "dateUpdated": "2026-10-19T08:50:29.852Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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