CVE-2026-97522

A flaw was found in the Linux kernel's MultiPath TCP (MPTCP) subsystem. When an error occurs while pushing pending data across subflows, the kernel improperly updates the transmitted byte counter with a negative error code instead of only accounting for successful transmissions. This accounting mismatch can cause subsequent push operations to fail and corrupt connection state, potentially resulting in a Denial of Service (DoS).

A low-impact flaw was found in the Linux kernel's MultiPath TCP (MPTCP) subsystem, affecting the kernel in Red Hat Enterprise Linux 9, Red Hat Enterprise Linux 10, Red Hat In-Vehicle OS, and OpenShift Container Platform releases built on RHEL CoreOS 9. When an error occurs while pending data is being pushed across MPTCP subflows, __mptcp_subflow_push_pending() incorrectly adds the negative error code returned by __subflow_push_pending() to the copied byte counter. This accounting mismatch can cause subsequent push operations on the affected MPTCP socket to fail and leave connection state inconsistent, allowing a local user who can create and transmit on MPTCP sockets to disrupt MPTCP connections, a denial of service limited to availability with no confidentiality or integrity impact. Red Hat assessed the impact as Low, lower than the Moderate severity implied by the CVSS 3.1 base score of 5.5 (AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H), because this is a local correctness problem in MPTCP byte accounting with no demonstrated memory-safety, privilege-escalation, or reliably exploitable kernel-crash primitive. The vulnerable code was introduced into Red Hat Enterprise Linux via the MPTCP "get_send" wrapper backport, so Red Hat Enterprise Linux 6, 7, and 8, RHEL 9.2 and earlier update streams, the corresponding kernel-rt builds, and OpenShift Container Platform releases based on RHEL CoreOS 8 are not affected because the vulnerable code is not present. For the affected streams, the fix is currently deferred to a future release; the residual risk is limited to local disruption of MPTCP connections.

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.

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.