CVE-2026-74636 tracing: Fix race between update_event_fields and, event_define_fields
A race condition in the Linux kernel tracing subsystem allows local attackers to cause a system crash by loading modules concurrently.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-74636?
CVE-2026-74636 is a vulnerability in Linux, published on 22 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official 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.
Which versions are affected by CVE-2026-74636?
How do I fix CVE-2026-74636?
Apply the vendor's patch.
Is CVE-2026-74636 being exploited?
There is no known exploitation of CVE-2026-74636 in the wild and no public exploit code.
Sources
Also known as AZL-97325, BELL-CVE-2026-74636, DEBIAN-CVE-2026-74636, GHSA-jcq2-873m-mp53, UBUNTU-CVE-2026-74636.