CVE-2026-99104 sched_ext: Fix the bypass dispatch claim for schedulers bypassed by an ancestor
- Exploited in the wild
- Not known
- Fix
- Available
What is CVE-2026-99104?
CVE-2026-99104 is a vulnerability in Linux, published on 28 Oct 2026.
Official description
In the Linux kernel, the following vulnerability has been resolved:
sched_ext: Fix the bypass dispatch claim for schedulers bypassed by an ancestor
scx_bypass() claims bypass dispatch when the scheduler's depth goes from zero to one and releases it when the depth returns to zero, but propagates only the depth to the descendants, not the claim. A descendant that starts bypassing with its ancestor never claims, and one whose own bypass ends under the ancestor's keeps its claim, as its depth does not return to zero.
A sub-scheduler enable whose bypass ends under a PM suspend thus leaks its claim: the parent keeps hosting bypass dispatch and the sub-scheduler's next bypass trips the WARN_ON_ONCE() on the claim. A sub-scheduler disable that starts under a PM suspend has no claim, so once the resume lifts the root's bypass its tasks sit on the parent's bypass DSQs with nobody consuming them.
Claim for every descendant whose depth goes from zero to one in the propagation and release every scheduler in the subtree whose depth returned to zero once the tasks have moved out of the bypass DSQs. A parent that is bypassing itself when a descendant claims consumes only its own bypass DSQs, empty until it leaves bypass and becomes the host.
Which versions are affected by CVE-2026-99104?
How do I fix CVE-2026-99104?
Upgrade to a fixed version.
Is CVE-2026-99104 being exploited?
There is no known exploitation of CVE-2026-99104 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-99104, GHSA-73px-7g6q-p2m6, UBUNTU-CVE-2026-99104.