CVE-2026-74731 sched_ext: Skip sub-disable teardown for never-linked sub-schedulers
A race condition in the Linux kernel scheduler allows a use-after-free, potentially leading to code execution or system crashes.
- 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-2026-74731?
CVE-2026-74731 is a high-severity use after free 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:
sched_ext: Skip sub-disable teardown for never-linked sub-schedulers
A sub-scheduler enable can fail before scx_link_sched() links the sched into the hierarchy, e.g. when the parent is already being disabled, and cleanup still runs the full scx_sub_disable().
That is racy against root disable: drain_descendants() is the only ordering between a sub's disable-time task walk and root disable's all-task teardown, and an unlinked sub is invisible to it. Root's teardown can thus run between the never-linked sub's drain and its walk, exiting every task to no scheduler.
The walk then trips the membership WARN and re-homes the exited tasks onto the dying hierarchy, a use-after-free.
Skip the cgroup ownership reset and the task walk if @sch was never linked, indicated by the empty ->sibling as unlinking only happens later in the same function. The membership WARN remains valid: a linked sub is always waited on by an ancestor's drain.
Which versions are affected by CVE-2026-74731?
How do I fix CVE-2026-74731?
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-2026-74731 being exploited?
There is no known exploitation of CVE-2026-74731 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-74731, GHSA-39hf-rf3c-rjqv, UBUNTU-CVE-2026-74731.