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CVE-2025-40307· NVD / CVE Program· CNA Linux

exfat: validate cluster allocation bits of the allocation bitmap

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.

HighCVSS 7.8 · v3.1—No exploit Fix available
Published
Dec 7, 2025
Updated
Aug 19, 2026
EPSS
0.1% · 3th percentile
CWE
—
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Report tools

JSON

Action score

31

Monitor

Low priority for now.

CVSS
31 / 40 · 7.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.1%

CNA vs NVD score

NVD
—
CNA · Linux
7.8
NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Affected systems

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Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • 5.7affected
    • 1acf1a564b6034b5af1e7fb23cb98cb3bb4f6003 and later · before 87f827d53bd0688597bda63ae95908e2ad39bac0affected · git
    • 1acf1a564b6034b5af1e7fb23cb98cb3bb4f6003 and later · before 67ce8034dc0278ddd88cad93d4218a945180ddddaffected · git
    • 1acf1a564b6034b5af1e7fb23cb98cb3bb4f6003 and later · before 6bc58b4c53795ab5fe00648344aa7d9d61175f90affected · git
    • 1acf1a564b6034b5af1e7fb23cb98cb3bb4f6003 and later · before 13c1d24803d5b0446b3f6f0fdd67e07ac1fdc7bfaffected · git
    • 1acf1a564b6034b5af1e7fb23cb98cb3bb4f6003 and later · before 79c1587b6cda74deb0c86fc7ba194b92958c793caffected · git
    • before 5.7not affected · semver
    • 6.1.183 and later · up to and including 6.1.*not affected · semver
    • 6.6.148 and later · up to and including 6.6.*not affected · semver
    • 6.12.58 and later · up to and including 6.12.*not affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.1.187-16.1.187-1
Debian:13linuxbefore 6.12.63-16.12.63-1
Debian:14linuxbefore 6.17.8-16.17.8-1

Same product

linux: all records

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Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux13c1d24803d5b0446b3f6f0fdd67e07ac1fdc7bfVendor (CNA)
Linux Linux67ce8034dc0278ddd88cad93d4218a945180ddddVendor (CNA)
Linux Linux6bc58b4c53795ab5fe00648344aa7d9d61175f90Vendor (CNA)
Linux Linux79c1587b6cda74deb0c86fc7ba194b92958c793cVendor (CNA)
Linux Linux87f827d53bd0688597bda63ae95908e2ad39bac0Vendor (CNA)
debian:linux6.1.187-1 · Debian:12Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

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Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

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CVSS vector

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

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Noroxi analysis

No Noroxi analysis for this record yet

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Change log

  1. Fix✗ → ✓

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References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records