FKIE_CVE-2026-31437

Vulnerability from fkie_nvd - Published: 2026-04-22 14:16 - Updated: 2026-06-17 10:33
Severity
5.5 (Medium) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: netfs: Fix NULL pointer dereference in netfs_unbuffered_write() on retry When a write subrequest is marked NETFS_SREQ_NEED_RETRY, the retry path in netfs_unbuffered_write() unconditionally calls stream->prepare_write() without checking if it is NULL. Filesystems such as 9P do not set the prepare_write operation, so stream->prepare_write remains NULL. When get_user_pages() fails with -EFAULT and the subrequest is flagged for retry, this results in a NULL pointer dereference at fs/netfs/direct_write.c:189. Fix this by mirroring the pattern already used in write_retry.c: if stream->prepare_write is NULL, skip renegotiation and directly reissue the subrequest via netfs_reissue_write(), which handles iterator reset, IN_PROGRESS flag, stats update and reissue internally.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/7a5482f5ce891decbf36f2e6fab1e9fc4a76a684Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/a4d1b4ba9754bac3efebd06f583a44a7af52c0abPatch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/e9075e420a1eb3b52c60f3b95893a55e77419ce8Patch
Impacted products
Vendor Product Version
linux linux_kernel *
linux linux_kernel *
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/netfs/direct_write.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "a4d1b4ba9754bac3efebd06f583a44a7af52c0ab",
              "status": "affected",
              "version": "72d08d2839649d1c5efbe375751f4473fa4486af",
              "versionType": "git"
            },
            {
              "lessThan": "7a5482f5ce891decbf36f2e6fab1e9fc4a76a684",
              "status": "affected",
              "version": "0c29f6d63122a0168d67cb8ecde5b4cf7fe4acb0",
              "versionType": "git"
            },
            {
              "lessThan": "e9075e420a1eb3b52c60f3b95893a55e77419ce8",
              "status": "affected",
              "version": "a0b4c7a49137ed21279f354eb59f49ddae8dffc2",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/netfs/direct_write.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "6.18.21",
              "status": "affected",
              "version": "6.18.17",
              "versionType": "semver"
            },
            {
              "lessThan": "6.19.11",
              "status": "affected",
              "version": "6.19.7",
              "versionType": "semver"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "configurations": [
    {
      "nodes": [
        {
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "3EF23CE5-8E2E-47D1-9B2C-449AA5BB1870",
              "versionEndExcluding": "6.18.21",
              "versionStartIncluding": "6.18.17",
              "vulnerable": true
            },
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "0F154E5F-DF7A-4EB9-BAFA-13EC093D679A",
              "versionEndExcluding": "6.19.11",
              "versionStartIncluding": "6.19.7",
              "vulnerable": true
            }
          ],
          "negate": false,
          "operator": "OR"
        }
      ]
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfs: Fix NULL pointer dereference in netfs_unbuffered_write() on retry\n\nWhen a write subrequest is marked NETFS_SREQ_NEED_RETRY, the retry path\nin netfs_unbuffered_write() unconditionally calls stream-\u003eprepare_write()\nwithout checking if it is NULL.\n\nFilesystems such as 9P do not set the prepare_write operation, so\nstream-\u003eprepare_write remains NULL. When get_user_pages() fails with\n-EFAULT and the subrequest is flagged for retry, this results in a NULL\npointer dereference at fs/netfs/direct_write.c:189.\n\nFix this by mirroring the pattern already used in write_retry.c: if\nstream-\u003eprepare_write is NULL, skip renegotiation and directly reissue\nthe subrequest via netfs_reissue_write(), which handles iterator reset,\nIN_PROGRESS flag, stats update and reissue internally."
    }
  ],
  "id": "CVE-2026-31437",
  "lastModified": "2026-06-17T10:33:43.237",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "LOCAL",
          "availabilityImpact": "HIGH",
          "baseScore": 5.5,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "LOW",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 1.8,
        "impactScore": 3.6,
        "source": "nvd@nist.gov",
        "type": "Primary"
      }
    ]
  },
  "published": "2026-04-22T14:16:36.980",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/7a5482f5ce891decbf36f2e6fab1e9fc4a76a684"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/a4d1b4ba9754bac3efebd06f583a44a7af52c0ab"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/e9075e420a1eb3b52c60f3b95893a55e77419ce8"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-476"
        }
      ],
      "source": "nvd@nist.gov",
      "type": "Primary"
    }
  ]
}


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