CVE-2026-89518
Low risk· EPSS 9%Exploitation Probability (EPSS)
Low risk9th percentile - higher than 9% of all known CVEs
Summary
A bug was fixed in the Linux kernel's sched_ext scheduler regarding dispatch kfuncs. Under core scheduling, ops.dispatch() may run on a different CPU than the dispatched rq, leading to incorrect assumptions in several kfunc paths, including a potential deadlock in scx_dsq_move() and incorrect resolution of SCX_DSQ_LOCAL.
Risk Assessment
The bug can cause a system deadlock or incorrect scheduler behavior, resulting in system hangs or instability, especially in environments with core scheduling enabled.
Recommendation
Update the Linux kernel to a version containing the fix for CVE-2026-89518. If possible, avoid using core scheduling until the update is applied.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: sched_ext: Fix this_rq() assumptions in dispatch kfuncs Under core scheduling, dispatch runs from within the core-wide pick and can target a sibling rq, so ops.dispatch() may execute on a CPU different from the dispatched rq's. Several kfunc paths assumed the two always coincide: - scx_dsq_move() decided whether an rq lock is held by testing this_rq()'s rq flags and lock-danced accordingly. A dispatch for a sibling took the unlocked-context branch and acquired the source rq lock on top of the already held dispatched rq lock which could deadlock. - scx_bpf_sub_dispatch() dispatched this_rq() with its stashed sub_dispatch_prev, which is NULL when dispatching for a sibling. - finish_dispatch(), scx_bpf_dsq_reenq() and scx_bpf_dsq_nr_queued() resolved SCX_DSQ_LOCAL to this CPU's local DSQ rather than the dispatched rq's. The latter two are callable from other rq-locked operations too, where SCX_DSQ_LOCAL now likewise resolves to the op's rq. This changes behavior also without core scheduling, e.g. for ops.enqueue() running a remote wakeup on the waking CPU, and is intended: which CPU happens to execute an operation is incidental, the op's rq is what it is operating on, and the resolution now matches the insert side where SCX_DSQ_LOCAL dispatches land on the task's rq. Use the rq tracked by scx_locked_rq(), which is set to the dispatched rq around ops invocations and NULL in unlocked contexts.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS