CVE-2026-89713

Full vulnerability record from the local CVENow database.

Description

In the Linux kernel, the following vulnerability has been resolved: NFSD: check truncate permission under inode lock nfsd_setattr() checks whether a size update needs NFSD_MAY_TRUNC before it takes inode_lock(). The comparison uses the file size sampled by that unlocked read, but the actual ATTR_SIZE update is applied later under inode_lock() by notify_change(). This leaves a TOCTOU window for append-only files. If a client sends a SETATTR that does not shrink the file at the time of the unlocked sample, a concurrent append can extend the file before nfsd_setattr() takes inode_lock(). notify_change() then applies a real truncation without the NFSD_MAY_TRUNC check that rejects IS_APPEND(inode). The VFS truncate syscall paths perform their own append-only checks before calling notify_change(), so NFSD must make this decision against the locked size it is about to change. Split the write-count acquisition from the truncation permission check. Keep get_write_access() before the locked setattr work, then recheck whether the requested size is below i_size_read(inode) after inode_lock() has been acquired and before notify_change(ATTR_SIZE). This also avoids the plain unlocked inode->i_size load.

Severity

CRITICAL

CVSS score

9.1 (v3.1)

Vulnerability status

Received

Source identifier

416baaa9-dc9f-4396-8d5f-8c081fb06d67

Published

2026-09-11 20:19:58.743000

Last modified

2026-10-30 13:20:27.270000

View original CVE JSON

{
  "id": "CVE-2026-89713",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "published": "2026-09-11T20:19:58.743",
  "lastModified": "2026-10-30T13:20:27.270",
  "vulnStatus": "Received",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nNFSD: check truncate permission under inode lock\n\nnfsd_setattr() checks whether a size update needs NFSD_MAY_TRUNC\nbefore it takes inode_lock(). The comparison uses the file size sampled\nby that unlocked read, but the actual ATTR_SIZE update is applied later\nunder inode_lock() by notify_change().\n\nThis leaves a TOCTOU window for append-only files. If a client sends a\nSETATTR that does not shrink the file at the time of the unlocked\nsample, a concurrent append can extend the file before nfsd_setattr()\ntakes inode_lock(). notify_change() then applies a real truncation\nwithout the NFSD_MAY_TRUNC check that rejects IS_APPEND(inode). The VFS\ntruncate syscall paths perform their own append-only checks before\ncalling notify_change(), so NFSD must make this decision against the\nlocked size it is about to change.\n\nSplit the write-count acquisition from the truncation permission check.\nKeep get_write_access() before the locked setattr work, then recheck\nwhether the requested size is below i_size_read(inode) after inode_lock()\nhas been acquired and before notify_change(ATTR_SIZE). This also avoids\nthe plain unlocked inode->i_size load."
    }
  ],
  "affected": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "affectedData": [
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "unaffected",
          "programFiles": [
            "fs/nfsd/vfs.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "783112f7401ff449d979530209b3f6c2594fdb4e",
              "lessThan": "0669861a2e8e2bdb9c1149417d8ad821996ae4fe",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "783112f7401ff449d979530209b3f6c2594fdb4e",
              "lessThan": "52d0c5bdfe232c9974d4b11f97078b9c7814f05d",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "783112f7401ff449d979530209b3f6c2594fdb4e",
              "lessThan": "3afa17d93ba8c925f49370c816c6dae5112d8c24",
              "versionType": "git",
              "status": "affected"
            },
            {
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              "versionType": "git",
              "status": "affected"
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            {
              "version": "783112f7401ff449d979530209b3f6c2594fdb4e",
              "lessThan": "44086254479035de42ca3d286ecf25521d4e6325",
              "versionType": "git",
              "status": "affected"
            },
            {
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              "lessThan": "b778e0e0a16759f22a70579c3cf8d254a40d4a7f",
              "versionType": "git",
              "status": "affected"
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            {
              "version": "604a3c407026d6162d15300478e63f901e435efc",
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            {
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              "versionType": "git",
              "status": "affected"
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            {
              "version": "3ee4f442e5b37a537297b812557b1163f96b5399",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "a3c6cbc4eac4473ed5461d5faae2794d3e5c0e44",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "982898d7f97a35447403c3fcecc0d96c646ce101",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "3.2.89",
              "lessThan": "3.3",
              "versionType": "semver",
              "status": "affected"
            },
            {
              "version": "3.16.44",
              "lessThan": "3.17",
              "versionType": "semver",
              "status": "affected"
            },
            {
              "version": "4.4.53",
              "lessThan": "4.5",
              "versionType": "semver",
              "status": "affected"
            },
            {
              "version": "4.9.14",
              "lessThan": "4.10",
              "versionType": "semver",
              "status": "affected"
            },
            {
              "version": "4.10.2",
              "lessThan": "4.11",
              "versionType": "semver",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "affected",
          "programFiles": [
            "fs/nfsd/vfs.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "4.11",
              "status": "affected"
            },
            {
              "version": "0",
              "lessThan": "4.11",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.1.191",
              "lessThanOrEqual": "6.1.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.6.160",
              "lessThanOrEqual": "6.6.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.12.109",
              "lessThanOrEqual": "6.12.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.18.50",
              "lessThanOrEqual": "6.18.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "7.2.4",
              "lessThanOrEqual": "7.2.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "7.3",
              "lessThanOrEqual": "*",
              "versionType": "original_commit_for_fix",
              "status": "unaffected"
            }
          ]
        }
      ]
    }
  ],
  "metrics": {
    "cvssMetricV31": [
      {
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary",
        "cvssData": {
          "version": "3.1",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H",
          "baseScore": 9.1,
          "baseSeverity": "CRITICAL",
          "attackVector": "NETWORK",
          "attackComplexity": "LOW",
          "privilegesRequired": "NONE",
          "userInteraction": "NONE",
          "scope": "UNCHANGED",
          "confidentialityImpact": "NONE",
          "integrityImpact": "HIGH",
          "availabilityImpact": "HIGH"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 5.2
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "timestamp": "2026-10-16T19:26:29.958634Z",
          "id": "CVE-2026-89713",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "version": "2.0.3"
        }
      }
    ]
  },
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/0669861a2e8e2bdb9c1149417d8ad821996ae4fe",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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}