CVE-2025-39840
- Published: 2025-09-19T16:15:42.703
In the Linux kernel, the following vulnerability has been resolved:
audit: fix out-of-bounds read in audit_compare_dname_path()
When a watch on dir=/ is combined with an fsnotify event for a
single-character name directly under / (e.g., creating /a), an
out-of-bounds read can occur in audit_compare_dname_path().
The helper parent_len() returns 1 for “/”. In audit_compare_dname_path(),
when parentlen equals the full path length (1), the code sets p = path + 1
and pathlen = 1 – 1 = 0. The subsequent loop then dereferences
p[pathlen – 1] (i.e., p[-1]), causing an out-of-bounds read.
Fix this by adding a pathlen > 0 check to the while loop condition
to prevent the out-of-bounds access.
[PM: subject tweak, sign-off email fixes]
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How to fix CVE-2025-39840
Description: In the Linux kernel, the following vulnerability has been resolved: audit: fix out-of-bounds read in audit_compare_dname_path() When a watch on dir=/ is combined with an fsnotify event for a single-character name directly under / (e.g., creating /a), an out-of-bounds read can occur in audit_compare_dname_path(). The helper parent_len() returns 1 for “/”. In audit_compare_dname_path(), when parentlen […]
Exploit Difficulty: HARD
⏱️ Time to exploit: > 4 hours
🛠️ Required skills: Advanced security expertise
💰 Public exploits: Rare or not public
How to Fix:
- Check if you're running the affected product
- Update to the latest patched version
- If patching is not immediately possible: restrict network exposure, apply least-privilege access
- Test the fix in a staging environment first
- Review logs for signs of exploitation
- Monitor for IOCs (Indicators of Compromise)
- Enable automatic security updates
- Set up vulnerability monitoring
- Review and harden security configurations
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