CVE-2026-90066 samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
A null pointer dereference in the Linux kernel ftrace sample module can cause a system crash during module unload if thread creation fails.
- 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-2026-90066?
CVE-2026-90066 is a vulnerability in Linux, published on 17 Sep 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:
samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
ftrace_direct_multi_init() assigns kthread_run()'s return value to simple_tsk without an IS_ERR() check. When kthread_run() fails it returns ERR_PTR(-ENOMEM), but init still returns 0, so the module loads with simple_tsk holding an error pointer. On unload, ftrace_direct_multi_exit() then passes that ERR_PTR to kthread_stop(), leading to a null-pointer-dereference.
Check the return value of kthread_run() with IS_ERR(); on failure, unregister the ftrace direct call and propagate the error code.
Which versions are affected by CVE-2026-90066?
How do I fix CVE-2026-90066?
Apply the vendor's patch.
Is CVE-2026-90066 being exploited?
There is no known exploitation of CVE-2026-90066 in the wild and no public exploit code.
Sources
Also known as AZL-102860, BELL-CVE-2026-90066, DEBIAN-CVE-2026-90066, GHSA-h42m-cfhq-9g8c, UBUNTU-CVE-2026-90066.