CVE-2025-40204: 
Linux Kernel vulnerability analysis and mitigation

CVE-2025-40204 is a security vulnerability in the Linux kernel's SCTP (Stream Control Transmission Protocol) implementation. The vulnerability was discovered and disclosed on November 12, 2025, affecting the MAC comparison functionality. The issue involves the way MACs are compared, which was not being done in constant time, potentially exposing the system to timing attacks (NVD).

The vulnerability exists in the SCTP implementation where MAC comparisons were not performed in constant time. To address this security concern, the fix implements the use of appropriate helper functions to ensure constant-time MAC comparisons, preventing potential timing-based attacks (NVD).

The vulnerability could potentially allow attackers to execute timing attacks against the SCTP implementation in the Linux kernel, potentially compromising the security of SCTP communications (NVD).

The vulnerability has been fixed in several Linux kernel versions. Debian has addressed the issue in version 6.17.7-2 for sid release, while version 6.1.158-1 contains the fix for the bookworm release. Other affected distributions are in the process of releasing patches (Debian Security).