VulnerabilityPublished 3 Nov 2026

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

Source GCVE Database

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Authoritative record:CVE-2026-99252· Medium

Not known to be exploited : upgrade to 8c94677e2b6145393d4c129fe0f5364b0e5000a5 when convenient.

Data as of 3 Nov 2026, 13:15 UTC

Severity

Medium

Rated Medium by Threat Radar's AI analysis · CVSS not yet scored by NVD

Thin evidence

One scorer or none

Patch: Available – fixed in 8c94677e2b6145393d4c129fe0f5364b0e5000a5

Exploitation evidence

Disclosed: evidence found.
CVE published 3 Nov 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 3 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

ghsa-qf92-wx54-fh27

What to do

Upgrade Linux kernel to 8c94677e2b6145393d4c129fe0f5364b0e5000a5.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ 50cb44bd0d5f243919a06b17b1d979fdcd72cb2b, < 8c94677e2b6145393d4c129fe0f5364b0e5000a5	Fixed in 8c94677e2b6145393d4c129fe0f5364b0e5000a5
LinuxLinux	Affected =7.2	Fixed in–
Red Hatredhat/kernel`pkg:rpm/redhat/kernel`Other threats	Affected =7.2	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A fix is available that disables preemption during the push operation in the mpscq queue. This limits the preemption window and prevents the consumer from spinning indefinitely. Users should apply the official Linux kernel update that includes this fix. No additional mitigation is required beyond applying the patch.

Description

A Linux kernel vulnerability in the io_uring/mpscq subsystem involves a race condition caused by preemption during a push operation. The issue arises because the producer can be preempted between making a node the new tail and linking it to its predecessor, leading to a consumer spinning indefinitely waiting for the producer to finish. This affects tasks that queue task_work for the ring, such as io-wq workers or message senders using IORING_OP_MSG_RING. The vulnerability is addressed by disabling preemption during the push to limit the window where the race can occur.

Impact

The impact is a potential hang or delay in consumer tasks that rely on the mpscq queue, caused by a producer being preempted in a critical section. This can degrade performance or responsiveness in affected Linux kernel subsystems using io_uring, particularly for tasks that queue work on the ring. There is no indication of privilege escalation or data corruption, but the issue can cause inefficient CPU usage and delays.

Summary

The vulnerability in the Linux kernel's io_uring/mpscq queue occurs because preemption is allowed between two critical steps in the push operation: setting the node as the new tail and linking it to its predecessor. If a producer task is preempted in this window and the consumer has higher priority on the same CPU, the consumer spins waiting for the producer to complete, but cond_resched() does not yield to the preempted producer. This can cause delays or hangs in consumers waiting for work completion. The fix involves disabling preemption during the push operation, bounding the window to interrupt time and preventing the consumer from spinning indefinitely.

References

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