CVE-2025-21893: keys: Fix UAF in key_put()

Severity: high (CVSS 7.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-03-31 · updated 2026-06-17
Weakness: CWE-416

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.

Affected products

Linux kernel: from 6.10 before 6.12.21; from 6.13 before 6.13.9; 6.14-rc1, 6.14-rc2, 6.14-rc3, 6.14-rc4 — fixed in 6.12.21, 6.13.9

How to fix

Upgrade to a fixed version: Linux kernel 6.12.21, 6.13.9. Check the vendor advisory for mitigations.

References

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