Vulnerability-Lookup

GHSA-H3HR-9QQW-CVG3

Vulnerability from github – Published: 2026-04-22 15:31 – Updated: 2026-04-22 15:31

Details

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.

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{
  "affected": [],
  "aliases": [
    "CVE-2026-31437"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-04-22T14:16:36Z",
    "severity": null
  },
  "details": "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": "GHSA-h3hr-9qqw-cvg3",
  "modified": "2026-04-22T15:31:40Z",
  "published": "2026-04-22T15:31:40Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-31437"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/7a5482f5ce891decbf36f2e6fab1e9fc4a76a684"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/a4d1b4ba9754bac3efebd06f583a44a7af52c0ab"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/e9075e420a1eb3b52c60f3b95893a55e77419ce8"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}

CVE-2026-31437 (GCVE-0-2026-31437)

Vulnerability from cvelistv5 – Published: 2026-04-22 13:53 – Updated: 2026-04-22 13:53

Title

netfs: Fix NULL pointer dereference in netfs_unbuffered_write() on retry

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.

Severity ?

No CVSS data available.

Assigner

Linux

References

URL

Tags

	https://git.kernel.org/stable/c/a4d1b4ba9754bac3e…
	https://git.kernel.org/stable/c/7a5482f5ce891decb…
	https://git.kernel.org/stable/c/e9075e420a1eb3b52…

Impacted products

Vendor

Product

Version

Linux

Affected: 72d08d2839649d1c5efbe375751f4473fa4486af , < a4d1b4ba9754bac3efebd06f583a44a7af52c0ab (git)
Affected: 0c29f6d63122a0168d67cb8ecde5b4cf7fe4acb0 , < 7a5482f5ce891decbf36f2e6fab1e9fc4a76a684 (git)
Affected: a0b4c7a49137ed21279f354eb59f49ddae8dffc2 , < e9075e420a1eb3b52c60f3b95893a55e77419ce8 (git)

Linux

Affected: 6.18.17 , < 6.18.21 (semver)
Affected: 6.19.7 , < 6.19.11 (semver)

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{
  "containers": {
    "cna": {
      "affected": [
        {
          "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"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.21",
                  "versionStartIncluding": "6.18.17",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.19.11",
                  "versionStartIncluding": "6.19.7",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "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."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-04-22T13:53:36.361Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
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        {
          "url": "https://git.kernel.org/stable/c/a4d1b4ba9754bac3efebd06f583a44a7af52c0ab"
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        {
          "url": "https://git.kernel.org/stable/c/7a5482f5ce891decbf36f2e6fab1e9fc4a76a684"
        },
        {
          "url": "https://git.kernel.org/stable/c/e9075e420a1eb3b52c60f3b95893a55e77419ce8"
        }
      ],
      "title": "netfs: Fix NULL pointer dereference in netfs_unbuffered_write() on retry",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
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  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-31437",
    "datePublished": "2026-04-22T13:53:36.361Z",
    "dateReserved": "2026-03-09T15:48:24.090Z",
    "dateUpdated": "2026-04-22T13:53:36.361Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date

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.

Detection rules are retrieved from Rulezet.

Action not permitted

GHSA-H3HR-9QQW-CVG3

CVE-2026-31437 (GCVE-0-2026-31437)

Tags

Sightings

Nomenclature