CVE-2026-43029

A flaw was found in the Linux kernel's Multipath TCP (mptcp) implementation. When an attacker sends data with MSG_PEEK | MSG_WAITALL flags, the system can enter a soft lockup state. This occurs because the sk_receive_queue is not properly cleared, causing the system to continuously find available data without actual waiting. This vulnerability can lead to a Denial of Service (DoS) condition, making the system unresponsive.

MPTCP recvmsg could soft-lockup under certain scheduling conditions; upstream fixes progress checks. Red Hat advises MPTCP users to update; optionally unload mptcp where the protocol is unused.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

To mitigate this issue, prevent the mptcp module from being loaded. See https://access.redhat.com/solutions/41278 for instructions.