CVE-2026-31481 tracing: Drain deferred trigger frees if kthread creation fails
A local attacker with kernel command line access can cause a kernel crash via null pointer dereference during boot-time trigger registration failures.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-31481?
CVE-2026-31481 is a medium-severity vulnerability in Linux kernel, published on 22 Apr 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: Drain deferred trigger frees if kthread creation fails
Boot-time trigger registration can fail before the trigger-data cleanup kthread exists. Deferring those frees until late init is fine, but the post-boot fallback must still drain the deferred list if kthread creation never succeeds.
Otherwise, boot-deferred nodes can accumulate on trigger_data_free_list, later frees fall back to synchronously freeing only the current object, and the older queued entries are leaked forever.
To trigger this, add the following to the kernel command line:
trace_event=sched_switch trace_trigger=sched_switch.traceon,sched_switch.traceon
The second traceon trigger will fail and be freed. This triggers a NULL pointer dereference and crashes the kernel.
Keep the deferred boot-time behavior, but when kthread creation fails, drain the whole queued list synchronously. Do the same in the late-init drain path so queued entries are not stranded there either.
Weakness: CWE-476
Which versions are affected by CVE-2026-31481?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-31481?
Apply the vendor's patch.
Is CVE-2026-31481 being exploited?
There is no known exploitation of CVE-2026-31481 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as DEBIAN-CVE-2026-31481, GHSA-vx7w-47r6-wxw3, UBUNTU-CVE-2026-31481.