crypto: af_alg - Disallow concurrent writes in af_alg_sendmsg
Prioritize patching. It under exploitation confirmed by CISA.
Official vendor statements in CSAF/VEX format: whether their product is affected, already fixed, or ruled out — and why. These are the vendor's assertions, not Vexday's judgment.
Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.
A flaw in the Linux kernel's cryptographic socket interface (af_alg) allows two processes to write data to the same socket simultaneously, causing the data to mix unpredictably and corrupt the socket's internal state. This can lead to incorrect cryptographic operations or crashes.
CVE-2025-39964 addresses a race condition (CWE-362) in af_alg_sendmsg where concurrent writes to the same af_alg socket lack serialization, resulting in data interleaving and state inconsistencies. The vulnerability is mitigated by introducing an exclusive write-ownership mechanism (ctx->write field) to enforce mutual exclusion on socket write operations.