CVE-2026-74636
Received Received - Intake

Race Condition in Linux Kernel Tracing Subsystem

Publication date: 2026-08-22

Last updated on: 2026-08-22

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: tracing: Fix race between update_event_fields and, event_define_fields The following sequence may leads race between event_define_fields() and update_event_fields(): CPU0 (loads module A) CPU1 (loads module B) =============================== =============================== load_module(A) load_module(B) notifier_call_chain notifier_call_chain trace_module_notify trace_module_notify mutex_lock(&event_mutex) trace_event_update_all() trace_module_add_events(A) down_write(&trace_event_sem) __register_event(call_A) __add_event_to_tracers(call_A) event_define_fields(call_A) for each f: list_for_each_entry(field, list_add(&f->link, &class->fields, link) &class->fields) field = class->fields->next; Where access to the class->fields is not protected by the event_mutex in trace_event_update_all(). This produces the following panic: Unable to handle kernel access ... at virtual address 0000000000000018 pc : update_event_fields+0xf8/0x368 Call trace: update_event_fields+0xf8/0x368 trace_event_update_all+0x7c/0x2b4 trace_module_notify+0x4c/0x1dc notifier_call_chain+0x84/0x168 blocking_notifier_call_chain_robust+0x64/0xd4 load_module+0x10c8/0x123c __arm64_sys_finit_module+0x230/0x31c Fix by taking event_mutex in trace_event_update_all() before trace_event_sem.

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Meta Information

Published
2026-08-22
Last Modified
2026-08-22
Generated
2026-08-22
AI Q&A
2026-08-22
EPSS Evaluated
N/A
NVD
CVE-2026-74636
EUVD
EUVD-2026-64573

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux_kernel linux_kernel *

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This is a race condition vulnerability in the Linux kernel's tracing subsystem. It occurs when two CPU cores attempt to modify the same kernel event data structure simultaneously without proper synchronization. The issue specifically involves the race between event_define_fields() and update_event_fields() functions during module loading, leading to a kernel panic and system crash.

Detection Guidance

This vulnerability is specific to the Linux kernel and may cause kernel panics. Detection requires checking kernel logs for traces of the described panic or race conditions in tracing subsystems. Use commands like dmesg | grep -i panic or journalctl -k | grep -i panic to inspect kernel logs for related errors.

Impact Analysis

This vulnerability can cause your Linux system to crash unexpectedly when certain modules are loaded, resulting in a kernel panic. The crash may lead to data loss, service disruption, or require a system reboot to recover. Systems relying on kernel tracing features are particularly affected.

Mitigation Strategies

Apply the kernel patch that fixes the race condition by ensuring event_mutex is taken in trace_event_update_all() before trace_event_sem. Update to a patched kernel version where this issue is resolved. Monitor kernel logs for any signs of the described panic after applying the patch.

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