# CVE-2026-99253: io_uring/cancel: rearm local work wake up before sleep

Status: published. Published: 2026-11-03. Updated: 2026-11-03.

In the Linux kernel, the following vulnerability has been resolved:

io_uring/cancel: rearm local work wake up before sleep

io_uring_try_cancel_requests() sets ->cq_wait_nr to 1 so that the next
io_req_local_work_add() wakes the cancelling task. The add that takes the
count to zero is the only one that wakes, later ones see a count <= 0 and
return. io_uring_cancel_generic() however only becomes
TASK_INTERRUPTIBLE much later, so the one wake up can be spent on a
running task. That is fine as long as the entry of that add is still
queued, as the io_local_work_pending() check then skips the sleep. It is
not if the add was delayed after queueing its entry:

CPU0 (submitter in exec or exit)      CPU1 (io_req_local_work_add)
                                      mpscq_push(req A)
io_uring_try_cancel_requests()
  io_run_local_work()  // runs req A
io_uring_try_cancel_requests()
  atomic_set(&ctx->cq_wait_nr, 1)
                                      atomic_read(&ctx->cq_wait_nr) == 1
                                      count taken, wake_up_state()
                                        // task is running, no-op
prepare_to_wait(TASK_INTERRUPTIBLE)
io_local_work_pending() == false
schedule()
                                      mpscq_push(req B)
                                      cq_wait_nr <= 0, return

Only the sleeping task can run req B, so it is stuck in execve() until a
signal happens to wake it. An exiting task doesn't even get that.

Arm the count again once the task state is set and before the work list
is checked, for the rings whose local work this task is the one to run.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- Linux / Linux: ≥ d46ab2c98ababa19b41a5709b6921d7b1add7f74; < aaa06bb9fc03384f7cf2dbc3e43f2939cc7791b2 (affected, git). Source: CNA: Linux
- Linux / Linux: 7.2 (affected); ≥ 0; < 7.2 (unaffected, semver); ≥ 7.2.14; ≤ 7.2.* (unaffected, semver). Source: CNA: Linux

## Severity and prioritization

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: Not reported

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://git.kernel.org/stable/c/aaa06bb9fc03384f7cf2dbc3e43f2939cc7791b2 (CNA: Linux)

## Provenance

- CNA: Linux: https://www.cve.org/CVERecord?id=CVE-2026-99253; retrieved 2026-11-03; source updated 2026-11-03

Revision: f633fdf81c0673ce4c1b69fd46d963a112c7c1bd36131d49b557591f742692a5

Canonical: https://y2.dev/cve/CVE-2026-99253

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