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CVE-2026-89658 (GCVE-0-2026-89658)

Vulnerability from cvelistv5 – Published: 2026-09-11 19:45 – Updated: 2026-09-13 06:32
VLAI
Title
NFSD: Prevent client use-after-free during NFSv4.0 revoked-state cleanup
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().
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: d688d8585e6bea5e4e37f7497feea93b6b0a469c , < 0ae0d2b5c5a1b39c0b3c15d96b32a5b0c583d519 (git)
Affected: d688d8585e6bea5e4e37f7497feea93b6b0a469c , < b413ec5b23e3445dc9c4f273116078e2d4747626 (git)
Affected: d688d8585e6bea5e4e37f7497feea93b6b0a469c , < 81cf7f1413862f87b078920c838460a6a88aa030 (git)
Affected: d688d8585e6bea5e4e37f7497feea93b6b0a469c , < 7b4f8a1586c42d3afc3c0ac779af2db7ab1a5c55 (git)
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Linux Linux Affected: 6.9
Unaffected: 0 , < 6.9 (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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{
  "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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          "vendor": "Linux",
          "versions": [
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              "version": "6.9"
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              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
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              "status": "unaffected",
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              "versionType": "semver"
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              "status": "unaffected",
              "version": "6.18.50",
              "versionType": "semver"
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              "status": "unaffected",
              "version": "7.2.4",
              "versionType": "semver"
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              "version": "7.3-rc1",
              "versionType": "original_commit_for_fix"
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.109",
                  "versionStartIncluding": "6.9",
                  "vulnerable": true
                },
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              "operator": "OR"
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        {
          "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()."
        }
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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 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": "2026-09-13T06:32:40.908Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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        {
          "url": "https://git.kernel.org/stable/c/7b4f8a1586c42d3afc3c0ac779af2db7ab1a5c55"
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89658",
    "datePublished": "2026-09-11T19:45:46.857Z",
    "dateReserved": "2026-09-11T19:38:34.743Z",
    "dateUpdated": "2026-09-13T06:32:40.908Z",
    "state": "PUBLISHED"
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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-09-15T18:29:44+00:00",
      "cve": "CVE-2026-89658",
      "id": "CVE-2026-89658",
      "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: Prevent client use-after-free during NFSv4.0 revoked-state cleanup",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89658.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "important",
      "current_release_date": "2026-09-16T00:00:56Z",
      "cve": "CVE-2026-89658",
      "id": "CVE-2026-89658",
      "initial_release_date": "2026-09-16T00:00:56Z",
      "product_status:known_affected": "29",
      "product_status:known_not_affected": "324",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-89658",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-89658.json",
      "version": "2"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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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.


Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.