CVE-2026-46173 exit: prevent preemption of oopsing TASK_DEAD task
A race condition in Linux kernel task exit handling allows use-after-free of task stacks, potentially leading to memory corruption and privilege escalation.
- 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-2026-46173?
CVE-2026-46173 is a high-severity use after free vulnerability in Linux kernel, published on 28 May 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:
exit: prevent preemption of oopsing TASK_DEAD task
When an already-exiting task oopses, make_task_dead() currently calls do_task_dead() with preemption enabled. That is forbidden: do_task_dead() calls __schedule(), which has a comment saying "WARNING: must be called with preemption disabled!".
If an oopsing task is preempted in do_task_dead(), between becoming TASK_DEAD and entering the scheduler explicitly, bad things happen: finish_task_switch() assumes that once the scheduler has switched away from a TASK_DEAD task, the task can never run again and its stack is no longer needed; but that assumption apparently doesn't hold if the dead task was preempted (the SM_PREEMPT case).
This means that the scheduler ends up repeatedly dropping references on the dead task's stack, which can lead to use-after-free or double-free of the entire task stack; in other words, two tasks can end up running on the same stack, resulting in various kinds of memory corruption.
(This does not just affect "recursively oopsing" tasks; it is enough to oops once during task exit, for example in a file_operations::release handler)
Which versions are affected by CVE-2026-46173?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-46173?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-46173 being exploited?
There is no known exploitation of CVE-2026-46173 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-89031, BELL-CVE-2026-46173, DEBIAN-CVE-2026-46173, GHSA-mpr4-2mm3-rwm6, ROOT-OS-DEBIAN-12-CVE-2026-46173, ROOT-OS-UBUNTU-2404-CVE-2026-46173 and 1 more.