CVE-2025-38491: 
Linux Kernel vulnerability analysis and mitigation

A vulnerability has been identified in the Linux kernel's MPTCP (Multipath TCP) implementation, tracked as CVE-2025-38491. The issue was discovered on July 28, 2025, and involves the non-atomic handling of fallback actions and decisions in the MPTCP protocol implementation. This vulnerability affects Linux kernel version 6.16.0-rc3 and potentially other versions (NVD).

The vulnerability stems from a race condition in the MPTCP protocol implementation where fallback actions and decisions are not handled atomically. The issue manifests in the mptcpdofallback function at net/mptcp/protocol.h:1244 and related code paths. The problem was initially detected through a Syzkaller-reported warning showing multiple CPU warnings at various points in the MPTCP protocol handling code (NVD).

The vulnerability could potentially affect the stability and reliability of MPTCP connections in the Linux kernel. When triggered, it causes kernel warnings and could potentially lead to system instability or denial of service conditions (NVD).

The issue has been addressed in the Linux kernel through patches that make the fallback action and fallback decision atomic. Three separate commits have been made to resolve this vulnerability (Kernel.org, Kernel.org, Kernel.org).