CVE-2026-98463 sched_ext: Derive SCX_RQ_IN_WAKEUP from the core enqueue flags
A use-after-free in the Linux kernel scheduler allows local attackers to execute arbitrary code or escalate privileges when sched_ext is enabled.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-98463?
CVE-2026-98463 is an use after free vulnerability in Linux, published on 18 Oct 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: Derive SCX_RQ_IN_WAKEUP from the core enqueue flags
schedule_deferred_locked() skips scheduling a deferred action while SCX_RQ_IN_WAKEUP is set and relies on the task_woken_scx() call that follows a wakeup enqueue to run it. enqueue_task_scx() sets the flag from the merged enqueue flags, which include the flags stashed for a remote activation. move_remote_task_to_local_dsq() thus sets SCX_RQ_IN_WAKEUP on the destination rq when the moved task was woken up, although no task_woken_scx() follows that activation.
An IMMED insert into a busy destination requests a local reenqueue during that enqueue. The request gets linked but not scheduled and stays pending until an unrelated wakeup or preemption on that CPU runs the deferred actions. The IMMED task sits behind the running task in the meantime. If nothing runs them before the scheduler is disabled, the request outlives the scheduler and points into its freed per-cpu area, which the next scheduler dereferences from run_deferred().
Test the core enqueue flags for the wakeup bit. Only the core's wakeup path is followed by task_woken_scx().
Which versions are affected by CVE-2026-98463?
How do I fix CVE-2026-98463?
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-2026-98463 being exploited?
There is no known exploitation of CVE-2026-98463 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-98463, DEBIAN-CVE-2026-98463, GHSA-7f2q-69qm-pp4c, UBUNTU-CVE-2026-98463.