CVE-2025-40022: crypto: af_alg - Fix incorrect boolean values in af_alg_ctx

Severity: unknown
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: 2025-10-24 · updated 2026-10-19

Description

In the Linux kernel, the following vulnerability has been resolved: crypto: af_alg - Fix incorrect boolean values in af_alg_ctx Commit 1b34cbbf4f01 ("crypto: af_alg - Disallow concurrent writes in af_alg_sendmsg") changed some fields from bool to 1-bit bitfields of type u32. However, some assignments to these fields, specifically 'more' and 'merge', assign values greater than 1. These relied on C's implicit conversion to bool, such that zero becomes false and nonzero becomes true. With a 1-bit bitfields of type u32 instead, mod 2 of the value is taken instead, resulting in 0 being assigned in some cases when 1 was intended. Fix this by restoring the bool type.

Affected products

Linux kernel: from 6.1.154 before 6.1.155; from 6.6.108 before 6.6.109; from 6.12.49 before 6.12.50; from 6.16.9 before 6.16.10 — fixed in 6.1.155, 6.12.50, 6.16.10, 6.6.109

How to fix

Upgrade to a fixed version: Linux kernel 6.1.155, 6.12.50, 6.16.10, 6.6.109. Check the vendor advisory for mitigations.

References

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