CVE-2026-74262

Received Received - Intake

KCM Socket Callback Race Condition in Linux Kernel

Publication date: 2026-08-15

Last updated on: 2026-08-17

Assigner: kernel.org

Description

In the Linux kernel, the following vulnerability has been resolved: kcm: use WRITE_ONCE() when changing lower socket callbacks kcm_attach() replaces a live lower TCP socket's sk_data_ready and sk_write_space callbacks with KCM handlers, and kcm_unattach() restores them later. Those callback-pointer updates are still plain stores even though the same fields can be read and invoked concurrently on other CPUs. If another CPU observes an older callback snapshot after the live field has already been restored, callback execution can run with a mismatched target and sk_user_data state, leading to stale or misdirected wakeups. Use WRITE_ONCE() for the callback replacement and restore operations so these shared callback fields follow the same visibility contract already established by the earlier 4022 fixes.

CVSS Scores

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Meta Information

Published

2026-08-15

Last Modified

2026-08-17

Generated

2026-09-04

AI Q&A

2026-08-15

EPSS Evaluated

2026-09-03

NVD

CVE-2026-74262

EUVD

EUVD-2026-59409

Affected Vendors & Products

Vendor	Product	Version / Range
linux	linux_kernel	*

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-UNKNOWN

Attack-Flow Graph

Executive Summary

This is a Linux kernel vulnerability where callback functions in a TCP socket are improperly updated without proper synchronization. The issue occurs when the kcm_attach and kcm_unattach functions replace and restore socket callbacks without using atomic operations. This can lead to race conditions where a CPU observes stale callback pointers, causing mismatched state and potential misdirected wakeups or execution.

Detection Guidance

This vulnerability is specific to the Linux kernel's KCM (Kernel Connection Multiplexor) subsystem. Detection requires checking if your kernel version includes the affected code path. Use uname -a to check your kernel version and compare it against patched versions. Look for kernel logs mentioning KCM or socket callback issues.

Impact Analysis

This vulnerability could cause system instability or crashes due to corrupted callback execution. It may lead to unexpected behavior in network operations, data corruption, or denial of service if exploited. Systems relying on the Linux kernel for networking could experience performance degradation or failures.

Compliance Impact

This vulnerability does not directly affect compliance with standards like GDPR or HIPAA as it is a low-level kernel issue involving socket callback synchronization. Compliance impacts would depend on system configuration and usage rather than the vulnerability itself.

Mitigation Strategies

Apply the latest kernel security updates from your Linux distribution. If no patch is available, consider disabling the KCM module by setting CONFIG_KCM=n in your kernel configuration and recompiling. Monitor kernel logs for suspicious activity related to socket callbacks.

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