CVE-2025-40307: exfat: validate cluster allocation bits of the allocation bitmap
Vulnerability summary
CVE-2025-40307 is a high (CVSS 7.8) vulnerability in linux. EPSS estimates a 0.15% chance of exploitation in the next 30 days, higher than 3.9% of scored vulnerabilities.
Not severe (CVSS 7.8, local access); no exploitation reported by the 5 checked sources
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 27 · Related 27Timeline
- 08-12-2025PublishedVulnerability first disclosed.
- 15-10-2026Last modifiedVulnerability information updated.
Description
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.
CVSS metrics
5 scores · 4 sources · 2 versions- OSV · UbuntuEcosystem advisory · calculated7.8HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- OSV · DebianEcosystem advisory · calculated7.8HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- NVDNIST7.8HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
EPSS trend
Probability
0.15%
Chance of exploitation in the next 30 days
Percentile
4%
Versus all other CVEs
30-day change
No change 0.00 pp
From 0.15% on 04-10-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeNo weakness data has been published for this record.
Affected systems
Known conditions: local access, low-privilege account, no user interaction (CVSS vector). Other conditions: not stated in public data.
Ubuntu142 products
- linuxAll versions (No fix recorded) | < 6.8.0-106.106 | < 6.17.0-14.14
- linux-allwinner-5.19All versions (No fix recorded)
- linux-awsAll versions (No fix recorded) | < 6.8.0-1050.53 | < 6.17.0-1007.7
- linux-aws-5.0All versions (No fix recorded)
- linux-aws-5.11All versions (No fix recorded)
Debian1 product
- linux< 6.1.187-1 | < 6.12.63-1 | < 6.17.8-1
Linux1 product
- linux≥ 1acf1a564b6034b5af1e7fb23cb98cb3bb4f6003, < 87f827d53bd0688597bda63ae95908e2ad39bac0 | ≥ 1acf1a564b6034b5af1e7fb23cb98cb3bb4f6003, < 67ce8034dc0278ddd88cad93d4218a945180dddd | ≥ 1acf1a564b6034b5af1e7fb23cb98cb3bb4f6003, < 6bc58b4c53795ab5fe00648344aa7d9d61175f90 | ≥ 1acf1a564b6034b5af1e7fb23cb98cb3bb4f6003, < 13c1d24803d5b0446b3f6f0fdd67e07ac1fdc7bf | ≥ 1acf1a564b6034b5af1e7fb23cb98cb3bb4f6003, < 79c1587b6cda74deb0c86fc7ba194b92958c793c | 5.7
3 vendors · 144 products
