CVE-2025-39964

A race condition was found in the Linux kernel cryptographic user API, AF_ALG in the way concurrent writes to the same AF_ALG socket are handled. Interleaved data and inconsistent internal socket state may result.

A local user could use this flaw to crash the system or corrupt cryptographic operation results, causing a denial of service or data integrity issues.

The AF_ALG datapath allowed two writers on the same socket, causing request payloads to interleave unpredictably and leaving the per-socket context inconsistent. The fix introduces an exclusive write ownership (ctx->write) so that only one writer can issue sendmsg() at a time, preventing state corruption.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.