CVE-2026-74262
Description
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 If another central processing unit (CPU) observes an outdated callback state, it can lead to mismatched callback execution and incorrect user data.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.
Statement
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 If another CPU observes an outdated callback snapshot after the live field has already been restored, callback execution can run with a mismatched target and sk_user_data state, causing stale or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.
Mitigation
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.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.5 | N/A | 7.8 |
| Attack Vector | Local | N/A | Local |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | Low | N/A | Low |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | High |
| Integrity Impact | None | N/A | High |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Understanding the Weakness (CWE)
Integrity,Other
Technical Impact: Alter Execution Logic; Unexpected State
The main problem is that -- if a lock is overcome -- data could be altered in a bad state.
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