CVE-2025-40287: exfat: fix improper check of dentry.stream.valid_size
Vulnerability summary
CVE-2025-40287 is a high (CVSS 7.1) vulnerability in linux. EPSS estimates a 0.18% chance of exploitation in the next 30 days, higher than 8.1% of scored vulnerabilities.
Not severe (CVSS 7.1, network access); no exploitation reported by the 5 checked sources
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 27 · Related 27Timeline
- 06-12-2025PublishedVulnerability first disclosed.
- 11-05-2026Last modifiedVulnerability information updated.
Description
In the Linux kernel, the following vulnerability has been resolved: exfat: fix improper check of dentry.stream.valid_size We found an infinite loop bug in the exFAT file system that can lead to a Denial-of-Service (DoS) condition. When a dentry in an exFAT filesystem is malformed, the following system calls — SYS_openat, SYS_ftruncate, and SYS_pwrite64 — can cause the kernel to hang. Root cause analysis shows that the size validation code in exfat_find() does not check whether dentry.stream.valid_size is negative. As a result, the system calls mentioned above can succeed and eventually trigger the DoS issue. This patch adds a check for negative dentry.stream.valid_size to prevent this vulnerability.
CVSS metrics
1 score · 1 source · 1 versionEPSS trend
Probability
0.18%
Chance of exploitation in the next 30 days
Percentile
8%
Versus all other CVEs
30-day change
No change 0.00 pp
From 0.18% 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: network-reachable, no authentication, user interaction (CVSS vector). Other conditions: not stated in public data.
Ubuntu154 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< 6.12.63-1 | < 6.17.9-1
Linux1 product
- linux≥ 11a347fb6cef62ce47e84b97c45f2b2497c7593b, < 6c627bcc1896ba62ec793d0c00da74f3c93ce3ad | ≥ 11a347fb6cef62ce47e84b97c45f2b2497c7593b, < 204b1b02ee018ba52ad2ece21fe3a8643d66a1b2 | ≥ 11a347fb6cef62ce47e84b97c45f2b2497c7593b, < 82ebecdc74ff555daf70b811d854b1f32a296bea | 6.8
3 vendors · 156 products
