Vulnerability-Lookup

FKIE_CVE-2025-40307

Vulnerability from fkie_nvd - Published: 2025-12-08 01:16 - Updated: 2026-08-19 17:18

Severity

7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Summary

In the Linux kernel, the following vulnerability has been resolved: exfat: validate cluster allocation bits of the allocation bitmap syzbot created an exfat image with cluster bits not set for the allocation bitmap. exfat-fs reads and uses the allocation bitmap without checking this. The problem is that if the start cluster of the allocation bitmap is 6, cluster 6 can be allocated when creating a directory with mkdir. exfat zeros out this cluster in exfat_mkdir, which can delete existing entries. This can reallocate the allocated entries. In addition, the allocation bitmap is also zeroed out, so cluster 6 can be reallocated. This patch adds exfat_test_bitmap_range to validate that clusters used for the allocation bitmap are correctly marked as in-use.

References

	URL	Tags
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/13c1d24803d5b0446b3f6f0fdd67e07ac1fdc7bf
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/67ce8034dc0278ddd88cad93d4218a945180dddd
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/6bc58b4c53795ab5fe00648344aa7d9d61175f90
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/79c1587b6cda74deb0c86fc7ba194b92958c793c
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/87f827d53bd0688597bda63ae95908e2ad39bac0

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/exfat/balloc.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "87f827d53bd0688597bda63ae95908e2ad39bac0",
              "status": "affected",
              "version": "1acf1a564b6034b5af1e7fb23cb98cb3bb4f6003",
              "versionType": "git"
            },
            {
              "lessThan": "67ce8034dc0278ddd88cad93d4218a945180dddd",
              "status": "affected",
              "version": "1acf1a564b6034b5af1e7fb23cb98cb3bb4f6003",
              "versionType": "git"
            },
            {
              "lessThan": "6bc58b4c53795ab5fe00648344aa7d9d61175f90",
              "status": "affected",
              "version": "1acf1a564b6034b5af1e7fb23cb98cb3bb4f6003",
              "versionType": "git"
            },
            {
              "lessThan": "13c1d24803d5b0446b3f6f0fdd67e07ac1fdc7bf",
              "status": "affected",
              "version": "1acf1a564b6034b5af1e7fb23cb98cb3bb4f6003",
              "versionType": "git"
            },
            {
              "lessThan": "79c1587b6cda74deb0c86fc7ba194b92958c793c",
              "status": "affected",
              "version": "1acf1a564b6034b5af1e7fb23cb98cb3bb4f6003",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/exfat/balloc.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.7"
            },
            {
              "lessThan": "5.7",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.183",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.148",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.58",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.17.*",
              "status": "unaffected",
              "version": "6.17.8",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "6.18",
              "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\nexfat: validate cluster allocation bits of the allocation bitmap\n\nsyzbot created an exfat image with cluster bits not set for the allocation\nbitmap. exfat-fs reads and uses the allocation bitmap without checking\nthis. The problem is that if the start cluster of the allocation bitmap\nis 6, cluster 6 can be allocated when creating a directory with mkdir.\nexfat zeros out this cluster in exfat_mkdir, which can delete existing\nentries. This can reallocate the allocated entries. In addition,\nthe allocation bitmap is also zeroed out, so cluster 6 can be reallocated.\nThis patch adds exfat_test_bitmap_range to validate that clusters used for\nthe allocation bitmap are correctly marked as in-use."
    }
  ],
  "id": "CVE-2025-40307",
  "lastModified": "2026-08-19T17:18:35.510",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "LOCAL",
          "availabilityImpact": "HIGH",
          "baseScore": 7.8,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 1.8,
        "impactScore": 5.9,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ]
  },
  "published": "2025-12-08T01:16:02.950",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/13c1d24803d5b0446b3f6f0fdd67e07ac1fdc7bf"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/67ce8034dc0278ddd88cad93d4218a945180dddd"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/6bc58b4c53795ab5fe00648344aa7d9d61175f90"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/79c1587b6cda74deb0c86fc7ba194b92958c793c"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/87f827d53bd0688597bda63ae95908e2ad39bac0"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Deferred"
}

CVE-2025-40307 (GCVE-0-2025-40307)

Vulnerability from cvelistv5 – Published: 2025-12-08 00:46 – Updated: 2026-08-19 16:27

Title

exfat: validate cluster allocation bits of the allocation bitmap

Summary

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

5 references

URL	Tags
https://git.kernel.org/stable/c/87f827d53bd068859…
https://git.kernel.org/stable/c/67ce8034dc0278ddd…
https://git.kernel.org/stable/c/6bc58b4c53795ab5f…
https://git.kernel.org/stable/c/13c1d24803d5b0446…
https://git.kernel.org/stable/c/79c1587b6cda74deb…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 1acf1a564b6034b5af1e7fb23cb98cb3bb4f6003 , < 87f827d53bd0688597bda63ae95908e2ad39bac0 (git) Affected: 1acf1a564b6034b5af1e7fb23cb98cb3bb4f6003 , < 67ce8034dc0278ddd88cad93d4218a945180dddd (git) Affected: 1acf1a564b6034b5af1e7fb23cb98cb3bb4f6003 , < 6bc58b4c53795ab5fe00648344aa7d9d61175f90 (git) Affected: 1acf1a564b6034b5af1e7fb23cb98cb3bb4f6003 , < 13c1d24803d5b0446b3f6f0fdd67e07ac1fdc7bf (git) Affected: 1acf1a564b6034b5af1e7fb23cb98cb3bb4f6003 , < 79c1587b6cda74deb0c86fc7ba194b92958c793c (git)
Linux	Linux	Affected: 5.7 Unaffected: 0 , < 5.7 (semver) Unaffected: 6.1.183 , ≤ 6.1.* (semver) Unaffected: 6.6.148 , ≤ 6.6.* (semver) Unaffected: 6.12.58 , ≤ 6.12.* (semver) Unaffected: 6.17.8 , ≤ 6.17.* (semver) Unaffected: 6.18 , ≤ * (original_commit_for_fix)

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/exfat/balloc.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "87f827d53bd0688597bda63ae95908e2ad39bac0",
              "status": "affected",
              "version": "1acf1a564b6034b5af1e7fb23cb98cb3bb4f6003",
              "versionType": "git"
            },
            {
              "lessThan": "67ce8034dc0278ddd88cad93d4218a945180dddd",
              "status": "affected",
              "version": "1acf1a564b6034b5af1e7fb23cb98cb3bb4f6003",
              "versionType": "git"
            },
            {
              "lessThan": "6bc58b4c53795ab5fe00648344aa7d9d61175f90",
              "status": "affected",
              "version": "1acf1a564b6034b5af1e7fb23cb98cb3bb4f6003",
              "versionType": "git"
            },
            {
              "lessThan": "13c1d24803d5b0446b3f6f0fdd67e07ac1fdc7bf",
              "status": "affected",
              "version": "1acf1a564b6034b5af1e7fb23cb98cb3bb4f6003",
              "versionType": "git"
            },
            {
              "lessThan": "79c1587b6cda74deb0c86fc7ba194b92958c793c",
              "status": "affected",
              "version": "1acf1a564b6034b5af1e7fb23cb98cb3bb4f6003",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/exfat/balloc.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.7"
            },
            {
              "lessThan": "5.7",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.183",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.148",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.58",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.17.*",
              "status": "unaffected",
              "version": "6.17.8",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "6.18",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.1.183",
                  "versionStartIncluding": "5.7",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.148",
                  "versionStartIncluding": "5.7",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.58",
                  "versionStartIncluding": "5.7",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.17.8",
                  "versionStartIncluding": "5.7",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18",
                  "versionStartIncluding": "5.7",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nexfat: validate cluster allocation bits of the allocation bitmap\n\nsyzbot created an exfat image with cluster bits not set for the allocation\nbitmap. exfat-fs reads and uses the allocation bitmap without checking\nthis. The problem is that if the start cluster of the allocation bitmap\nis 6, cluster 6 can be allocated when creating a directory with mkdir.\nexfat zeros out this cluster in exfat_mkdir, which can delete existing\nentries. This can reallocate the allocated entries. In addition,\nthe allocation bitmap is also zeroed out, so cluster 6 can be reallocated.\nThis patch adds exfat_test_bitmap_range to validate that clusters used for\nthe allocation bitmap are correctly marked as in-use."
        }
      ],
      "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 code is reached by getting a crafted exFAT image mounted from a local block device, loop file, or removable medium and then issuing a local `mkdir()`; there is no network consumer of `exfat_allocate_bitmap()`.\nAC:L - The attacker fully controls the image: clearing the bitmap\u0027s own allocation bit and pointing `start_clu` at a low cluster makes `exfat_find_free_bitmap()` deterministically return that cluster on the very first allocation, so a single `mkdir` reliably zeroes the live bitmap with no race, heap shaping, or memory-layout dependency.\nPR:L - Direct `mount()` needs CAP_SYS_ADMIN, but ubiquitous privileged mount brokers (udisks2, systemd-mount, autofs, Android vold) let an unprivileged local user get an attacker-supplied exFAT volume or loop image mounted rw, after which any user with write access to the mount can run the triggering `mkdir`.\nUI:N - The attacker requests the mount through the automount broker and runs `mkdir` themselves; on a kiosk or shared workstation inserting their own exFAT stick achieves the same, with no action required from any other user or administrator.\nS:U - The corruption and its consequences are confined to the kernel and filesystem that own the mount; no VM, IOMMU, container, or other security-authority boundary is crossed.\nC:H - Once the bitmap is zeroed the allocator re-hands out clusters that are still live, so a newly created file is backed by clusters holding the root directory, other files\u0027 data, and the allocation bitmap itself \u2014 reading that file discloses their full contents, an unbounded read of co-resident data on the shared volume rather than a small bounded leak.\nI:H - This is the core defect: the kernel zeroes and overwrites in-use on-disk metadata (\"can delete existing entries\") and reallocates already-allocated clusters, so attacker-controlled file writes land directly in directory entries and in the live in-kernel allocation bitmap, giving unbounded modification of structures the filesystem subsequently trusts.\nA:H - The zeroed bitmap makes every `exfat_clear_bitmap()` fail with `-EIO`, desyncs `used_clusters` into `exfat_fs_error_ratelimit()`, and produces aliased/looping cluster chains that yield task hangs and the syzbot-reported deadlock WARNING; with `errors=panic`, `panic_on_warn`, or `panic_on_oops` this is a full panic, and the volume is left permanently unusable."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-19T16:27:52.404Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/87f827d53bd0688597bda63ae95908e2ad39bac0"
        },
        {
          "url": "https://git.kernel.org/stable/c/67ce8034dc0278ddd88cad93d4218a945180dddd"
        },
        {
          "url": "https://git.kernel.org/stable/c/6bc58b4c53795ab5fe00648344aa7d9d61175f90"
        },
        {
          "url": "https://git.kernel.org/stable/c/13c1d24803d5b0446b3f6f0fdd67e07ac1fdc7bf"
        },
        {
          "url": "https://git.kernel.org/stable/c/79c1587b6cda74deb0c86fc7ba194b92958c793c"
        }
      ],
      "title": "exfat: validate cluster allocation bits of the allocation bitmap",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2025-40307",
    "datePublished": "2025-12-08T00:46:32.659Z",
    "dateReserved": "2025-04-16T07:20:57.185Z",
    "dateUpdated": "2026-08-19T16:27:52.404Z",
    "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.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.