CVE-2026-74262

A flaw was found in the Linux kernel's Kernel Connection Multiplexor (KCM) module. This vulnerability occurs due to a race condition when the KCM module replaces or restores lower TCP socket callbacks. If another central processing unit (CPU) observes an outdated callback state, it can lead to mismatched callback execution and incorrect user data. This could result in stale or misdirected wakeups, potentially causing system instability or a denial of service.

A MODERATE severity race condition was found in the Linux kernel's Kernel Connection Multiplexor (KCM) module. When a KCM socket is attached, kcm_attach() replaces the lower TCP socket's sk_data_ready and sk_write_space callbacks with KCM handlers, and kcm_unattach() later restores them; those callback-pointer updates are performed as plain, unsynchronized stores even though the same fields can be read and invoked concurrently on other CPUs. If another CPU observes an outdated callback snapshot after the live field has already been restored, callback execution can run with a mismatched target and sk_user_data state, causing stale or misdirected wakeups, data inconsistency, and potential system instability or denial of service. A local user with privileges to use KCM sockets could trigger this race condition. Red Hat rates this flaw MODERATE because the impact is limited to availability of the affected socket (CVSS 5.5, CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H), which differs from the upstream CVEORG score of 7.8 (IMPORTANT) that additionally assumes high confidentiality and integrity impact not supported by the technical evidence. All currently assessed Red Hat Enterprise Linux and Red Hat In-Vehicle OS kernel, kernel-rt, and kernel-ivos-qualcomm components are marked not affected because the vulnerable code is not present in the shipped versions.

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.