CVE-2026-97523

A flaw was found in the Linux kernel's MultiPath TCP (MPTCP) subsystem. A race condition between the packet scheduler and socket state transitions can cause the maximum segment size to be reset to zero following a transmission failure. An attacker could exploit this flaw during connection handling to trigger a division-by-zero error during socket release, leading to a kernel crash and a Denial of Service (DoS).

A moderate-impact race condition flaw was found in the Linux kernel's MultiPath TCP (MPTCP) subsystem. If the MPTCP packet scheduler races with a subflow socket state change, data transmission on the selected subflow can fail and leave the maximum segment size (mss_now) reset to zero; a subsequent socket release can then perform a division by zero in tcp_push(), causing a kernel panic and a denial of service. An unprivileged local user who can create and transmit data on MPTCP sockets and win this timing-dependent race can crash the system; confidentiality and integrity are not affected. Red Hat Enterprise Linux 6 and 7 are not affected because the vulnerable code is not present. The kernel packages in Red Hat Enterprise Linux 8, 9, and 10, Red Hat In-Vehicle OS, and the RHEL CoreOS kernels used by OpenShift Container Platform are affected, with fixes currently deferred; no fixed packages are available at this time, and the residual risk is local denial of service on systems where untrusted local users can use MPTCP sockets. Red Hat rates this flaw moderate (CVSS 5.5, AV:L/AC:L/PR:L) rather than the upstream 7.5 network severity, because triggering the race requires local execution of MPTCP socket operations on the affected host.

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.