A denial of service vulnerability in the Linux kernel mptcp subsystem allows unauthenticated attackers to cause CPU exhaustion and system instability.

This is a denial of service flaw caused by a soft lockup in the mptcp_recvmsg function, triggered when receiving data with MSG_PEEK and MSG_WAITALL flags without proper tracking, requiring no attacker authentication.

A successful exploit can lead to a severe denial of service, rendering affected systems unresponsive and requiring hard reboots due to CPU core lockups. This disrupts business operations and impacts service availability. The CVSS score of 7.5 reflects the high impact on system availability despite requiring no user interaction or privileges.

Immediate Action: Update the Linux kernel to version 6.18.22, 6.19.12, or later where the mptcp receive queue tracking issue is resolved.

Proactive Monitoring: Monitor system logs for kernel watchdogs reporting CPU soft lockups or stuck tasks related to mptcp_recvmsg and server processes.

Compensating Controls: Implement network-level rate limiting or firewall rules to restrict untrusted traffic targeting MPTCP endpoints if immediate kernel patching is not feasible.

Public Exploit Available: Yes, a published PoC exists, as indicated by the syzbot report reference detailing the reproduction steps and kernel traceback.

Administrators must treat this high severity availability issue with urgency by scheduling kernel updates as soon as possible. Applying the vendor patches prevents potential denial of service attacks that could destabilize critical server infrastructure.