Linux Kernel af_alg Socket: Disallow Concurrent Write Race
CVE-2025-39964 Published on October 13, 2025
crypto: af_alg - Disallow concurrent writes in af_alg_sendmsg
In the Linux kernel, the following vulnerability has been resolved:
crypto: af_alg - Disallow concurrent writes in af_alg_sendmsg
Issuing two writes to the same af_alg socket is bogus as the
data will be interleaved in an unpredictable fashion. Furthermore,
concurrent writes may create inconsistencies in the internal
socket state.
Disallow this by adding a new ctx->write field that indiciates
exclusive ownership for writing.
Weakness Type
What is a Race Condition Vulnerability?
The program contains a code sequence that can run concurrently with other code, and the code sequence requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence that is operating concurrently.
CVE-2025-39964 has been classified to as a Race Condition vulnerability or weakness.
Products Associated with CVE-2025-39964
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Affected Versions
Linux:- Version 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 and below 0f28c4adbc4a97437874c9b669fd7958a8c6d6ce is affected.
- Version 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 and below e4c1ec11132ec466f7362a95f36a506ce4dc08c9 is affected.
- Version 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 and below 1f323a48e9b5ebfe6dc7d130fdf5c3c0e92a07c8 is affected.
- Version 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 and below 7c4491b5644e3a3708f3dbd7591be0a570135b84 is affected.
- Version 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 and below 9aee87da5572b3a14075f501752e209801160d3d is affected.
- Version 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 and below 45bcf60fe49b37daab1acee57b27211ad1574042 is affected.
- Version 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 and below 1b34cbbf4f011a121ef7b2d7d6e6920a036d5285 is affected.
- Version 2.6.38 is affected.
- Before 2.6.38 is unaffected.
- Version 5.10.245, <= 5.10.* is unaffected.
- Version 5.15.194, <= 5.15.* is unaffected.
- Version 6.1.154, <= 6.1.* is unaffected.
- Version 6.6.108, <= 6.6.* is unaffected.
- Version 6.12.49, <= 6.12.* is unaffected.
- Version 6.16.9, <= 6.16.* is unaffected.
- Version 6.17, <= * is unaffected.
- Version V3.1.6 and below * is affected.
- Version V3.1.6 and below * is affected.
- Version V3.1.6 and below * is affected.
- Version V3.1.6 and below * is affected.
- Version V3.1.6 and below * is affected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.