CVE-2026-90432 sched_ext: Abort directly from the hardlockup handler
A flaw in the Linux kernel's sched_ext subsystem can cause hard lockups, leading to a 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-2026-90432?
CVE-2026-90432 is a denial of service vulnerability in Linux, published on 17 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: Abort directly from the hardlockup handler
scx_hardlockup() defers the abort to an irq_work because exit claiming used to take scx_sched_lock and couldn't run from NMI. The deferral is now unnecessary - claiming is NMI-safe and asserting ->aborting is exactly what breaks the live-locks that hard-lock CPUs. Call handle_lockup() directly and drop the irq_work. This also makes the self-detected case recoverable: the perf watchdog fires on the hard-locked CPU itself, where a queued irq_work never runs with IRQs off.
Also fix the return value: %true used to be returned whenever sched_ext was loaded, suppressing the kernel's hardlockup report even when the abort was refused. Return %true only when this call initiated the abort.
Which versions are affected by CVE-2026-90432?
How do I fix CVE-2026-90432?
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-2026-90432 being exploited?
There is no known exploitation of CVE-2026-90432 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-90432, GHSA-3xgc-q8gm-m2rg, UBUNTU-CVE-2026-90432.