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CVE-2025-39840

7.1 · HIGH

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 sing…

Published Sep 19, 2025CWE-125EPSS 0.15%

Overview

CVE-2025-39840 is a high-severity vulnerability. It was published on September 19, 2025 and has a CVSS 3.1 base score of 7.1 (HIGH).

This vulnerability has a CVSS 3.1 base score of 7.1, rated HIGH. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.

Technical 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 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]

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

Refgit.kernel.org/stable/c/4540f1d23e7f387880ce46d11b5cd3f27248bf8dRefgit.kernel.org/stable/c/9735a9dcc307427e7d6336c54171682f1bac9789

How CyberStrike helps

Frequently asked questions

What is CVE-2025-39840?

CVE-2025-39840 is a high-severity vulnerability. It was published on September 19, 2025 and has a CVSS 3.1 base score of 7.1 (HIGH).

How severe is CVE-2025-39840?

This vulnerability has a CVSS 3.1 base score of 7.1, rated HIGH. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.

How do I fix or remediate CVE-2025-39840?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2025-39840?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2025-39840 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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