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CVE-2025-21893

7.8 · HIGH

In the Linux kernel, the following vulnerability has been resolved: keys: Fix UAF in key_put() Once a key's reference count has been reduced to 0, the garbage collector thread may destroy it at a…

Published Mar 31, 2025CWE-416EPSS 0.20%

Overview

CVE-2025-21893 is a high-severity vulnerability. It was published on March 31, 2025 and has a CVSS 3.1 base score of 7.8 (HIGH).

This vulnerability has a CVSS 3.1 base score of 7.8, 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:

keys: Fix UAF in key_put()

Once a key's reference count has been reduced to 0, the garbage collector

thread may destroy it at any time and so key_put() is not allowed to touch

the key after that point. The most key_put() is normally allowed to do is

to touch key_gc_work as that's a static global variable.

However, in an effort to speed up the reclamation of quota, this is now

done in key_put() once the key's usage is reduced to 0 - but now the code

is looking at the key after the deadline, which is forbidden.

Fix this by using a flag to indicate that a key can be gc'd now rather than

looking at the key's refcount in the garbage collector.

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/6afe2ea2daec156bd94ad2c5a6f4f4c48240dcd3Refgit.kernel.org/stable/c/75845c6c1a64483e9985302793dbf0dfa5f71e32Refgit.kernel.org/stable/c/f6a3cf833188e897c97028cd7b926e3f2cb1a8c0

How CyberStrike helps

Frequently asked questions

What is CVE-2025-21893?

CVE-2025-21893 is a high-severity vulnerability. It was published on March 31, 2025 and has a CVSS 3.1 base score of 7.8 (HIGH).

How severe is CVE-2025-21893?

This vulnerability has a CVSS 3.1 base score of 7.8, 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-2025-21893?

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-2025-21893?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2025-21893 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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