CVE-2026-89519 sched_ext: Replace SCX_RQ_BAL_KEEP with a dispatch verdict return
A race condition in the Linux kernel's sched_ext scheduler can cause a stale flag to keep a dequeued task running, potentially leading to system instability or denial of service.
- 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-2026-89519?
CVE-2026-89519 is a vulnerability in Linux, published on 11 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:
sched_ext: Replace SCX_RQ_BAL_KEEP with a dispatch verdict return
SCX_RQ_BAL_KEEP tells the pick to keep running the previous task, a leftover from when balancing and picking were separate operations. An rq-level flag only works while dispatches and picks pair up one to one, which core scheduling breaks: selections interleave through dispatch's lock drops and a pick can consume a stale flag, keeping a task that has since been dequeued. Fixing core scheduling support requires the decision to travel with the dispatch that made it. Make scx_dispatch_sched() and balance_one() return an explicit verdict instead and drop the flag's plumbing from the tools autogen enum headers.
Also factor the pick-side invocation, its follow-up queueing and the post-dispatch checks out of do_pick_task_scx() into dispatch_pick(). No functional changes intended.
v2: Drop the SCX_RQ_BAL_KEEP plumbing from the tools autogen enum headers as well (Andrea).
Which versions are affected by CVE-2026-89519?
How do I fix CVE-2026-89519?
Apply the vendor's patch.
Is CVE-2026-89519 being exploited?
There is no known exploitation of CVE-2026-89519 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-89519, GHSA-4vmj-w324-pvrj, UBUNTU-CVE-2026-89519.