CVE-2026-89685 (GCVE-0-2026-89685)

Vulnerability from cvelistv5 – Published: 2026-09-11 19:46 – Updated: 2026-10-30 12:32
VLAI
Title
nfsd: fix clock domain mismatch in clients_still_reclaiming()
Summary
In the Linux kernel, the following vulnerability has been resolved: nfsd: fix clock domain mismatch in clients_still_reclaiming() clients_still_reclaiming() computes a deadline from nn->boot_time (CLOCK_REALTIME, ~1.7 billion) but compares it against ktime_get_boottime_seconds() (CLOCK_BOOTTIME, seconds since boot). The comparison is always false — it would take ~54 years of uptime for BOOTTIME to exceed the REALTIME-derived deadline. This means any client can hold the server in grace indefinitely by sending CLAIM_PREVIOUS OPEN requests, blocking all non-reclaim operations for all other clients. Add boot_time_bt (CLOCK_BOOTTIME) alongside the existing boot_time and use it for the deadline computation. boot_time (CLOCK_REALTIME) is preserved for its cl_boot clientid-nonce role.
Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
SSVC
Exploitation: none Automatable: yes Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-10-16 19:25 UTC
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6971 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 20b7d86f29d39e8ae19bb29c24ffee70dc385ddf , < 7ca44a63d9a554ba7ad05b06d88746eab08b760e (git)
Affected: 20b7d86f29d39e8ae19bb29c24ffee70dc385ddf , < 2c9efc6b692a153643d0f204b3c3632cb6b5761e (git)
Affected: 20b7d86f29d39e8ae19bb29c24ffee70dc385ddf , < a22ee3a2cadef44f2edeb909ae36bd72450a3a35 (git)
Affected: 20b7d86f29d39e8ae19bb29c24ffee70dc385ddf , < 04c3e4456fe76e8d7c94171009df3165c3262c51 (git)
Affected: 20b7d86f29d39e8ae19bb29c24ffee70dc385ddf , < e92e80c5b043108029bc729b30d12c37158fb9cb (git)
Affected: 20b7d86f29d39e8ae19bb29c24ffee70dc385ddf , < f9cec313efb2fd18d962aad738a4892bce806016 (git)
Affected: 20b7d86f29d39e8ae19bb29c24ffee70dc385ddf , < 9843649196221152b6e5d138a3ce859bdaae1d96 (git)
Affected: 20b7d86f29d39e8ae19bb29c24ffee70dc385ddf , < 09ea3eb9a518565f5bca386e81b993ed8825f5e8 (git)
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Linux Linux Affected: 5.6
Unaffected: 0 , < 5.6 (semver)
Unaffected: 5.10.273 , ≤ 5.10.* (semver)
Unaffected: 5.15.224 , ≤ 5.15.* (semver)
Unaffected: 6.1.191 , ≤ 6.1.* (semver)
Unaffected: 6.6.160 , ≤ 6.6.* (semver)
Unaffected: 6.12.111 , ≤ 6.12.* (semver)
Unaffected: 6.18.51 , ≤ 6.18.* (semver)
Unaffected: 7.2.4 , ≤ 7.2.* (semver)
Unaffected: 7.3 , ≤ * (original_commit_for_fix)
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            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: fix clock domain mismatch in clients_still_reclaiming()\n\nclients_still_reclaiming() computes a deadline from nn-\u003eboot_time\n(CLOCK_REALTIME, ~1.7 billion) but compares it against\nktime_get_boottime_seconds() (CLOCK_BOOTTIME, seconds since boot).\nThe comparison is always false \u2014 it would take ~54 years of uptime\nfor BOOTTIME to exceed the REALTIME-derived deadline.\n\nThis means any client can hold the server in grace indefinitely by\nsending CLAIM_PREVIOUS OPEN requests, blocking all non-reclaim\noperations for all other clients.\n\nAdd boot_time_bt (CLOCK_BOOTTIME) alongside the existing boot_time\nand use it for the deadline computation. boot_time (CLOCK_REALTIME)\nis preserved for its cl_boot clientid-nonce role."
          }
        ],
        "id": "CVE-2026-89685",
        "lastModified": "2026-10-30T13:20:26.333",
        "metrics": {
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                "attackVector": "NETWORK",
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                "baseScore": 7.5,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "NONE",
                "integrityImpact": "NONE",
                "privilegesRequired": "NONE",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
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        "published": "2026-09-11T20:19:55.420",
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        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
      }
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    "redhat_vex": {
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      "current_release_date": "2026-10-30T15:11:08+00:00",
      "cve": "CVE-2026-89685",
      "id": "CVE-2026-89685",
      "initial_release_date": "2026-09-11T00:00:00+00:00",
      "product_status:known_affected": "251",
      "product_status:known_not_affected": "28",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: nfsd: fix clock domain mismatch in clients_still_reclaiming()",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89685.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-10-27T00:57:40Z",
      "cve": "CVE-2026-89685",
      "id": "CVE-2026-89685",
      "initial_release_date": "2026-09-12T16:23:43Z",
      "product_status:known_affected": "658",
      "product_status:known_not_affected": "143",
      "product_status:recommended": "164",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-89685",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/2026/cve-2026-89685.json",
      "version": "11"
    },
    "vulnrichment": {
      "containers": {
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            "metrics": [
              {
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                  "content": {
                    "id": "CVE-2026-89685",
                    "options": [
                      {
                        "Exploitation": "none"
                      },
                      {
                        "Automatable": "yes"
                      },
                      {
                        "Technical Impact": "partial"
                      }
                    ],
                    "role": "CISA Coordinator",
                    "timestamp": "2026-10-16T19:25:59.702339Z",
                    "version": "2.0.3"
                  },
                  "type": "ssvc"
                }
              }
            ],
            "providerMetadata": {
              "dateUpdated": "2026-10-16T19:26:00.471Z",
              "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
              "shortName": "CISA-ADP"
            },
            "title": "CISA ADP Vulnrichment"
          }
        ],
        "cna": {
          "affected": [
            {
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              "product": "Linux",
              "programFiles": [
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              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "vendor": "Linux",
              "versions": [
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              "vendor": "Linux",
              "versions": [
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                  "version": "0",
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                  "status": "unaffected",
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                {
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                  "status": "unaffected",
                  "version": "5.15.224",
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                {
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                  "status": "unaffected",
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                {
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                  "status": "unaffected",
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                  "status": "unaffected",
                  "version": "6.12.111",
                  "versionType": "semver"
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                {
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                  "status": "unaffected",
                  "version": "6.18.51",
                  "versionType": "semver"
                },
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                  "status": "unaffected",
                  "version": "7.2.4",
                  "versionType": "semver"
                },
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                  "status": "unaffected",
                  "version": "7.3",
                  "versionType": "original_commit_for_fix"
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              "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: fix clock domain mismatch in clients_still_reclaiming()\n\nclients_still_reclaiming() computes a deadline from nn-\u003eboot_time\n(CLOCK_REALTIME, ~1.7 billion) but compares it against\nktime_get_boottime_seconds() (CLOCK_BOOTTIME, seconds since boot).\nThe comparison is always false \u2014 it would take ~54 years of uptime\nfor BOOTTIME to exceed the REALTIME-derived deadline.\n\nThis means any client can hold the server in grace indefinitely by\nsending CLAIM_PREVIOUS OPEN requests, blocking all non-reclaim\noperations for all other clients.\n\nAdd boot_time_bt (CLOCK_BOOTTIME) alongside the existing boot_time\nand use it for the deadline computation. boot_time (CLOCK_REALTIME)\nis preserved for its cl_boot clientid-nonce role."
            }
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                  "value": "AV:N - nfsd processes NFSv4 COMPOUND OPEN over TCP (typically port 2049). A remote peer reaches clients_still_reclaiming() by sending CLAIM_PREVIOUS OPEN or reclaim LOCK, which sets NFSD_NET_SOMEBODY_RECLAIMED and prevents grace from ending.\nAC:L - The attacker fully controls the reclaim OPEN/LOCK RPCs that keep NFSD_NET_SOMEBODY_RECLAIMED set; no race or memory layout is required. Grace always starts with nfsd, and the broken REALTIME-vs-BOOTTIME deadline never fires, so the attacker can extend it at will.\nPR:N - Default nfsd exports accept AUTH_SYS/AUTH_NULL with no credentials. An unauthenticated network peer that is or becomes a recorded NFSv4 client can send CLAIM_PREVIOUS OPEN; no server account or capability is required.\nUI:N - Exploitation takes only attacker-sent NFSv4 RPCs after nfsd starts; no victim user action such as mounting or opening a file is required.\nS:U - The impact stays in the same kernel nfsd/lockd grace state. This is a service denial on the NFS server, not a VM, IOMMU, or sandbox boundary crossing.\nC:N - The bug only miscompares grace deadlines and extends the grace period. It does not disclose kernel memory or file contents.\nI:N - No unauthorized modification of kernel or file data occurs. Other clients are blocked from new mutating operations, which is an availability effect rather than an integrity violation.\nA:H - Successful reclaim OPENs hold nfsd in grace indefinitely because the double-lease deadline never expires, so non-reclaim OPEN/REMOVE/RENAME/SETXATTR and lockd grace return NFS4ERR_GRACE and fully deny NFSv4 service to other clients."
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            "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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        "assignerShortName": "Linux",
        "cveId": "CVE-2026-89685",
        "datePublished": "2026-09-11T19:46:07.116Z",
        "dateReserved": "2026-09-11T19:38:34.749Z",
        "dateUpdated": "2026-10-30T12:32:41.984Z",
        "state": "PUBLISHED"
      },
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      "dataVersion": "5.2"
    }
  }
}



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Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
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  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
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Vulnerability timeline

Sightings and recorded dates, grouped by day · UTC

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