CVE-2026-98865 sched_ext: Don't run ops.dequeue() with a DSQ lock held
A local attacker with BPF scheduler privileges can cause a kernel deadlock by triggering a self-deadlock in the sched_ext subsystem.
- 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-2026-98865?
CVE-2026-98865 is a denial of service 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: Don't run ops.dequeue() with a DSQ lock held
ops.dequeue() is invoked with the source user DSQ's lock still held on the consume and move paths (scx_consume_dispatch_q(), move_task_between_dsqs()). A BPF scheduler which locks the source user DSQ from ops.dequeue() - e.g. by iterating it with bpf_iter_scx_dsq - self-deadlocks.
ops.dequeue() can only call the "any" kfuncs and none of them can lock a builtin DSQ, so the global and bypass paths can't deadlock; however, all DSQ locks share one lockdep class, so iterating any user DSQ from ops.dequeue() on those paths trips the recursion check.
Move the invocation after the DSQ unlock on all three paths. SCX_TASK_IN_CUSTODY is cleared under the lock serializing the transfer so that the callback is invoked exactly once.
Which versions are affected by CVE-2026-98865?
How do I fix CVE-2026-98865?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-98865 being exploited?
There is no known exploitation of CVE-2026-98865 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-98865, GHSA-2w8f-349m-66qf, UBUNTU-CVE-2026-98865.