CVE-2025-40022
Low risk· EPSS 9%Exploitation Probability (EPSS)
Low risk9th percentile - higher than 9% of all known CVEs
Summary
In the Linux kernel's cryptographic subsystem (af_alg), a bug was found where incorrect boolean values were assigned to 1-bit bitfields of type u32. The 'more' and 'merge' fields received values greater than 1, which were truncated modulo 2 in 1-bit bitfields, resulting in 0 being set instead of the intended 1.
Risk Assessment
This vulnerability may cause incorrect behavior of cryptographic operations in the kernel, potentially leading to data processing errors or integrity violations in encryption operations. It could affect applications using the af_alg interface, including the security of encrypted communications.
Recommendation
Immediately update the Linux kernel to a version containing the fix (commit restoring the bool type for 'more' and 'merge' fields). Monitor official kernel distributions and apply the security patch.
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Original NVD description (English source)
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.

