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Vulnerabilities

Vulnerability · CVE-2026-99252

CVE-2026-99252: io_uring/mpscq: disable preemption while pushing

Published Nov 3, 2026 · catalog updated Nov 3, 2026 · Linux Linux Kernel

Last checked Nov 7, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2026-99252. EPSS is 0.18%. Act only if a listed version of Linux Linux Kernel is installed.

Gaps on this record

  • No version range is stored. A customer cannot check an installed version against this record.
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.

Same product and reporting

Severity
Unknown—
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.18%
Remediation
Not established
Affected products
linux kernel · vendor Linux Linux

In the Linux kernel, the following vulnerability has been resolved: io_uring/mpscq: disable preemption while pushing A push makes the node the new tail, and then links it to its predecessor. In between the queue isn't empty, but mpscq_pop() can't get at the node. The consumers deal with that by trying again, with a cond_resched() in the loop to give a preempted producer the chance to finish. cond_resched() doesn't do that if the consumer has a higher priority than the producer and both have to use the same CPU: producer (SCHED_OTHER) consumer (SCHED_FIFO), same CPU io_req_local_work_add() mpscq_push() prev = xchg(&q->tail, node) io_cqring_wait() __io_run_local_work() again: cond_resched() // nothing to do mpscq_pop() // NULL // work pending, no events yet goto again The producer can be any task that is able to queue task_work for the ring: an io-wq worker, or somebody who sends a message with IORING_OP_MSG_RING. The consumer spins, holding ->uring_lock, until the scheduler takes pity on the fair class, which takes about a second with the default settings of the fair server, and forever without it. The loops in tctx_task_work_run() and io_cancel_local_task_work() have the same problem. Don't allow preemption between the two steps. That bounds the time the window is open on the CPU of the producer by what interrupts take, and a consumer that waits for that is on another CPU. The cost is a preempt_disable()/preempt_enable() pair per push.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

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  • linux kernelversion unspecified
  • vendor Linux Linuxversion unspecified

How to fix CVE-2026-99252

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-99252. EPSS is 0.18%. Act only if a listed version of Linux Linux Kernel is installed.

Which versions are affected?

Affected version ranges are not on this record. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

No weakness class is stored. EPSS 0.18%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Nov 3, 2026 · Linux Kernel CVE

    Detected

    From: Greg Kroah-Hartman Description =========== In the Linux kernel, the following vulnerability has been resolved: io_uring/mpscq: disable preemption while pushing A push makes the node the new tail, and then links it to its predecessor. In between the queue isn't empty, but mpscq_pop() can't get at the node. The consumers deal with that by trying again, with a cond_resched() in the loop to give

  2. Nov 3, 2026 · CVE.org

    Updated

    In the Linux kernel, the following vulnerability has been resolved: io_uring/mpscq: disable preemption while pushing A push makes the node the new tail, and then links it to its predecessor. In between the queue isn't empty, but mpscq_pop() can't get at the node. The consumers deal with that by trying again, with a cond_resched() in the loop to give a preempted producer the chance to finish. cond_

Sources

  • CVE.orgVulnerability recordCVE-2026-99252

    In the Linux kernel, the following vulnerability has been resolved: io_uring/mpscq: disable preemption while pushing A push makes the node the new tail, and then links it to its predecessor. In between the queue isn't empty, but mpscq_pop() can't get at the node. The consumers de

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-99252

    30-day exploitation probability 0.18%

    first.org
  • Linux Kernel CVEVendor advisoryCVE-2026-99252

    CVE-2026-99252 has now been rejected and is no longer a valid CVE.

    git.kernel.org

References

Freshness

Last verified in this catalog Nov 4, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • Linux Kernel CVENov 7, 2026
  • FIRST EPSSNov 4, 2026
  • CVE.orgNov 4, 2026