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GHSA-8FXX-FJ7Q-42M6

Vulnerability from github – Published: 2026-05-01 15:30 – Updated: 2026-06-01 18:31

Details

In the Linux kernel, the following vulnerability has been resolved:

fuse: reject oversized dirents in page cache

fuse_add_dirent_to_cache() computes a serialized dirent size from the server-controlled namelen field and copies the dirent into a single page-cache page. The existing logic only checks whether the dirent fits in the remaining space of the current page and advances to a fresh page if not. It never checks whether the dirent itself exceeds PAGE_SIZE.

As a result, a malicious FUSE server can return a dirent with namelen=4095, producing a serialized record size of 4120 bytes. On 4 KiB page systems this causes memcpy() to overflow the cache page by 24 bytes into the following kernel page.

Reject dirents that cannot fit in a single page before copying them into the readdir cache.

Severity

7.8 (High)


                  
                    CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

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{
  "affected": [],
  "aliases": [
    "CVE-2026-31694"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-05-01T14:16:19Z",
    "severity": "HIGH"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nfuse: reject oversized dirents in page cache\n\nfuse_add_dirent_to_cache() computes a serialized dirent size from the\nserver-controlled namelen field and copies the dirent into a single\npage-cache page. The existing logic only checks whether the dirent fits\nin the remaining space of the current page and advances to a fresh page\nif not. It never checks whether the dirent itself exceeds PAGE_SIZE.\n\nAs a result, a malicious FUSE server can return a dirent with\nnamelen=4095, producing a serialized record size of 4120 bytes. On 4 KiB\npage systems this causes memcpy() to overflow the cache page by 24 bytes\ninto the following kernel page.\n\nReject dirents that cannot fit in a single page before copying them into\nthe readdir cache.",
  "id": "GHSA-8fxx-fj7q-42m6",
  "modified": "2026-06-01T18:31:28Z",
  "published": "2026-05-01T15:30:32Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-31694"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/038e61812fa52ef62bad2cfc96bf37dc0db47c1e"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/1d4a517fa90480c52fd452fea2686cd80f773ce2"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/3059f9abe7f1ba8fddf3c86c5faa1eeacf07e7d4"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/45c05af36311624c1148123caeb011312495d86b"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/474ce83c96a55f2eeb14dee2be375eeadfdacdf5"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/51a8de6c50bf947c8f534cd73da4c8f0a13e7bed"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/7de93abfaae1b2dc94da8a07a36421bd073f1d8f"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/d23ad78bfd205eac26766e38ba7d79f279131098"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2026-31694 (GCVE-0-2026-31694)

Vulnerability from cvelistv5 – Published: 2026-05-01 13:53 – Updated: 2026-08-05 12:24

Title

fuse: reject oversized dirents in page cache

Summary

In the Linux kernel, the following vulnerability has been resolved: fuse: reject oversized dirents in page cache fuse_add_dirent_to_cache() computes a serialized dirent size from the server-controlled namelen field and copies the dirent into a single page-cache page. The existing logic only checks whether the dirent fits in the remaining space of the current page and advances to a fresh page if not. It never checks whether the dirent itself exceeds PAGE_SIZE. As a result, a malicious FUSE server can return a dirent with namelen=4095, producing a serialized record size of 4120 bytes. On 4 KiB page systems this causes memcpy() to overflow the cache page by 24 bytes into the following kernel page. Reject dirents that cannot fit in a single page before copying them into the readdir cache.

Severity

7.8 (High)


                        
                          CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Assigner

Linux mitre root

References

3 references

URL	Tags
https://git.kernel.org/stable/c/7de93abfaae1b2dc9…
https://git.kernel.org/stable/c/474ce83c96a55f2ee…
https://git.kernel.org/stable/c/51a8de6c50bf947c8…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 27992ef80770d61a57f6c3a551735b08cefdffa3 , < 7de93abfaae1b2dc94da8a07a36421bd073f1d8f (git) Affected: 27992ef80770d61a57f6c3a551735b08cefdffa3 , < 474ce83c96a55f2eeb14dee2be375eeadfdacdf5 (git) Affected: 27992ef80770d61a57f6c3a551735b08cefdffa3 , < 51a8de6c50bf947c8f534cd73da4c8f0a13e7bed (git)
Linux	Linux	Affected: 6.15 Unaffected: 0 , < 6.15 (semver) Unaffected: 6.18.25 , ≤ 6.18.* (semver) Unaffected: 7.0.2 , ≤ 7.0.* (semver) Unaffected: 7.1 , ≤ * (original_commit_for_fix)

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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/fuse/readdir.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "7de93abfaae1b2dc94da8a07a36421bd073f1d8f",
              "status": "affected",
              "version": "27992ef80770d61a57f6c3a551735b08cefdffa3",
              "versionType": "git"
            },
            {
              "lessThan": "474ce83c96a55f2eeb14dee2be375eeadfdacdf5",
              "status": "affected",
              "version": "27992ef80770d61a57f6c3a551735b08cefdffa3",
              "versionType": "git"
            },
            {
              "lessThan": "51a8de6c50bf947c8f534cd73da4c8f0a13e7bed",
              "status": "affected",
              "version": "27992ef80770d61a57f6c3a551735b08cefdffa3",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/fuse/readdir.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.15"
            },
            {
              "lessThan": "6.15",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.25",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.0.*",
              "status": "unaffected",
              "version": "7.0.2",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.25",
                  "versionStartIncluding": "6.15",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.0.2",
                  "versionStartIncluding": "6.15",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.1",
                  "versionStartIncluding": "6.15",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nfuse: reject oversized dirents in page cache\n\nfuse_add_dirent_to_cache() computes a serialized dirent size from the\nserver-controlled namelen field and copies the dirent into a single\npage-cache page. The existing logic only checks whether the dirent fits\nin the remaining space of the current page and advances to a fresh page\nif not. It never checks whether the dirent itself exceeds PAGE_SIZE.\n\nAs a result, a malicious FUSE server can return a dirent with\nnamelen=4095, producing a serialized record size of 4120 bytes. On 4 KiB\npage systems this causes memcpy() to overflow the cache page by 24 bytes\ninto the following kernel page.\n\nReject dirents that cannot fit in a single page before copying them into\nthe readdir cache."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The vulnerable path is reached through local filesystem operations on a FUSE mount, with malicious replies supplied via a local /dev/fuse userspace daemon rather than directly by network packets.\nAC:L - A malicious FUSE server can deterministically set FOPEN_CACHE_DIR and return a dirent with namelen=4095; the overflow occurs during ordinary readdir/getdents on common 4 KiB page systems.\nPR:L - An unprivileged local user can plausibly run and access their own FUSE filesystem, including through user-namespace-capable FUSE mounts where available, and does not need real init-namespace root.\nUI:N - The malicious local mounter can trigger getdents/readdir on their own FUSE directory without requiring a separate victim action.\nS:U - The bug is kernel memory corruption within the same host kernel security authority and does not cross a VM, IOMMU, or similar scope boundary.\nC:H - The bug is an attacker-controlled out-of-bounds write into the following kernel page, and such kernel memory corruption can be leveraged to expose sensitive kernel or process memory.\nI:H - The attacker controls the oversized serialized dirent bytes copied past the cache page, giving a kernel memory corruption primitive that can plausibly be developed into arbitrary modification or code execution.\nA:H - The overflow can corrupt adjacent kernel memory or fault during the memcpy/kmap access path, making kernel oops, panic, or system instability a high-impact availability outcome."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:24:32.263Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
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          "url": "https://git.kernel.org/stable/c/7de93abfaae1b2dc94da8a07a36421bd073f1d8f"
        },
        {
          "url": "https://git.kernel.org/stable/c/474ce83c96a55f2eeb14dee2be375eeadfdacdf5"
        },
        {
          "url": "https://git.kernel.org/stable/c/51a8de6c50bf947c8f534cd73da4c8f0a13e7bed"
        }
      ],
      "title": "fuse: reject oversized dirents in page cache",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-31694",
    "datePublished": "2026-05-01T13:53:36.048Z",
    "dateReserved": "2026-03-09T15:48:24.131Z",
    "dateUpdated": "2026-08-05T12:24:32.263Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

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.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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GHSA-8FXX-FJ7Q-42M6

CVE-2026-31694 (GCVE-0-2026-31694)

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