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

Vulnerability from cvelistv5 – Published: 2026-09-11 19:46 – Updated: 2026-09-13 06:33
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
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux 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: 6.18.51 , ≤ 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/netns.h",
            "fs/nfsd/nfs4state.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "f9cec313efb2fd18d962aad738a4892bce806016",
              "status": "affected",
              "version": "20b7d86f29d39e8ae19bb29c24ffee70dc385ddf",
              "versionType": "git"
            },
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              "status": "affected",
              "version": "20b7d86f29d39e8ae19bb29c24ffee70dc385ddf",
              "versionType": "git"
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            "fs/nfsd/nfs4state.c"
          ],
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          "vendor": "Linux",
          "versions": [
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              "status": "affected",
              "version": "5.6"
            },
            {
              "lessThan": "5.6",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
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              "version": "6.18.51",
              "versionType": "semver"
            },
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                  "vulnerable": true
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              ],
              "negate": false,
              "operator": "OR"
            }
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      "descriptions": [
        {
          "lang": "en",
          "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."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.5,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          },
          "scenarios": [
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              "lang": "en",
              "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."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-13T06:33:08.546Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/f9cec313efb2fd18d962aad738a4892bce806016"
        },
        {
          "url": "https://git.kernel.org/stable/c/9843649196221152b6e5d138a3ce859bdaae1d96"
        },
        {
          "url": "https://git.kernel.org/stable/c/09ea3eb9a518565f5bca386e81b993ed8825f5e8"
        }
      ],
      "title": "nfsd: fix clock domain mismatch in clients_still_reclaiming()",
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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": "2026-09-13T06:33:08.546Z",
    "state": "PUBLISHED"
  },
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  "dataVersion": "5.2",
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      "percentile": "0.36563"
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      "cve": "CVE-2026-89685",
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      "initial_release_date": "2026-09-13T01:09:30.000Z",
      "product_status:known_affected": "1",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "nfsd: fix clock domain mismatch in clients_still_reclaiming()",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-89685.json",
      "version": "2"
    },
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    "redhat_vex": {
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      "current_release_date": "2026-09-13T07:00:42+00:00",
      "cve": "CVE-2026-89685",
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      "cve": "CVE-2026-89685",
      "id": "CVE-2026-89685",
      "initial_release_date": "2026-09-12T16:23:43Z",
      "product_status:known_affected": "210",
      "product_status:known_not_affected": "143",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-89685",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-89685.json",
      "version": "5"
    }
  }
}



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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.

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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.


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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.