FKIE_CVE-2026-89711

Vulnerability from fkie_nvd - Published: 2026-09-11 20:19 - Updated: 2026-10-19 09:18
Severity
8.2 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: NFSD: remove flawed WARN_ON_ONCE from nfsd_mode_check The header for commit e75b23f9e323 ("nfsd: check d_can_lookup in fh_verify of directories") details the assumption that justified adding the WARN_ON_ONCE to nfsd_mode_check(), that assumption is invalid (in the case of NFS reexport). When NFSD exports an NFS filesystem it is very possible for nfsd_mode_check() to encounter a @dentry that doesn't have i_op->lookup (see nfs_fhget()'s NFS_ATTR_FATTR_MOUNTPOINT and NFS_ATTR_FATTR_V4_REFERRAL handling, and d_flags_for_inode()). So remove nfsd_mode_check()'s WARN_ON_ONCE(). The nfserr_notdir return on that branch must stay. It guards the subsequent lookup_one_unlocked() -> __lookup_slow() path, which calls inode->i_op->lookup() with no NULL check, so returning nfserr_notdir is what keeps a client LOOKUP into such a @dentry from dereferencing a NULL method pointer.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/2ef131323999539038e306773c8256403834361b
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/7ef182a8fe9c12b0d936880b1e504840639aa009
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/9f4434893a2783f7384d993cea883aff3fb7a52d
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/a275de3bac5635514ca830f2e46b5ff0e66b5c4c
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/aa0cf48a448c5a9fe1a1e880899ecd589ce39e6e
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/ae251937c6f0237e5b555a5e4ba4595b8206e865
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/b55b4d880bb080fa10eb08ba21a5d8679b8102fe
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/e145e8d67a5d41c72d322e7f87ab474d39d9dfb7
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/nfsd/nfsfh.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "ae251937c6f0237e5b555a5e4ba4595b8206e865",
              "status": "affected",
              "version": "e75b23f9e323b1e0759619c39d5a9f7a3a5d9d2c",
              "versionType": "git"
            },
            {
              "lessThan": "e145e8d67a5d41c72d322e7f87ab474d39d9dfb7",
              "status": "affected",
              "version": "e75b23f9e323b1e0759619c39d5a9f7a3a5d9d2c",
              "versionType": "git"
            },
            {
              "lessThan": "9f4434893a2783f7384d993cea883aff3fb7a52d",
              "status": "affected",
              "version": "e75b23f9e323b1e0759619c39d5a9f7a3a5d9d2c",
              "versionType": "git"
            },
            {
              "lessThan": "2ef131323999539038e306773c8256403834361b",
              "status": "affected",
              "version": "e75b23f9e323b1e0759619c39d5a9f7a3a5d9d2c",
              "versionType": "git"
            },
            {
              "lessThan": "b55b4d880bb080fa10eb08ba21a5d8679b8102fe",
              "status": "affected",
              "version": "e75b23f9e323b1e0759619c39d5a9f7a3a5d9d2c",
              "versionType": "git"
            },
            {
              "lessThan": "7ef182a8fe9c12b0d936880b1e504840639aa009",
              "status": "affected",
              "version": "e75b23f9e323b1e0759619c39d5a9f7a3a5d9d2c",
              "versionType": "git"
            },
            {
              "lessThan": "a275de3bac5635514ca830f2e46b5ff0e66b5c4c",
              "status": "affected",
              "version": "e75b23f9e323b1e0759619c39d5a9f7a3a5d9d2c",
              "versionType": "git"
            },
            {
              "lessThan": "aa0cf48a448c5a9fe1a1e880899ecd589ce39e6e",
              "status": "affected",
              "version": "e75b23f9e323b1e0759619c39d5a9f7a3a5d9d2c",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/nfsd/nfsfh.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "4.8"
            },
            {
              "lessThan": "4.8",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.10.*",
              "status": "unaffected",
              "version": "5.10.270",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.221",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.188",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.157",
              "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"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nNFSD: remove flawed WARN_ON_ONCE from nfsd_mode_check\n\nThe header for commit e75b23f9e323 (\"nfsd: check d_can_lookup in\nfh_verify of directories\") details the assumption that justified\nadding the WARN_ON_ONCE to nfsd_mode_check(), that assumption is\ninvalid (in the case of NFS reexport).\n\nWhen NFSD exports an NFS filesystem it is very possible for\nnfsd_mode_check() to encounter a @dentry that doesn\u0027t have\ni_op-\u003elookup (see nfs_fhget()\u0027s NFS_ATTR_FATTR_MOUNTPOINT and\nNFS_ATTR_FATTR_V4_REFERRAL handling, and d_flags_for_inode()).\n\nSo remove nfsd_mode_check()\u0027s WARN_ON_ONCE(). The nfserr_notdir\nreturn on that branch must stay. It guards the subsequent\nlookup_one_unlocked() -\u003e __lookup_slow() path, which calls\ninode-\u003ei_op-\u003elookup() with no NULL check, so returning nfserr_notdir\nis what keeps a client LOOKUP into such a @dentry from dereferencing\na NULL method pointer."
    }
  ],
  "id": "CVE-2026-89711",
  "lastModified": "2026-10-19T09:18:09.960",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 8.2,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "LOW",
          "integrityImpact": "NONE",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 4.2,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-89711",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-10-16T19:26:26.232461Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-09-11T20:19:58.500",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/2ef131323999539038e306773c8256403834361b"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/7ef182a8fe9c12b0d936880b1e504840639aa009"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/9f4434893a2783f7384d993cea883aff3fb7a52d"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/a275de3bac5635514ca830f2e46b5ff0e66b5c4c"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/aa0cf48a448c5a9fe1a1e880899ecd589ce39e6e"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/ae251937c6f0237e5b555a5e4ba4595b8206e865"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/b55b4d880bb080fa10eb08ba21a5d8679b8102fe"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/e145e8d67a5d41c72d322e7f87ab474d39d9dfb7"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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