VulnerabilityPublished 3 Nov 2026

CVE-2026-99254: Linux kernel · io_uring: don't flood a cancelling task with task_work

Source GCVE Database

Compare

Authoritative record:CVE-2026-99254· Medium

Not known to be exploited · fixed in abdc57c7ebabaaf0b622178a6a85834e1e54ff80 : update Linux kernel when convenient.

Data as of 3 Nov 2026, 13:16 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 abdc57c7ebabaaf0b622178a6a85834e1e54ff80, a22fb44e988b01b82235ea07f0bf0fc73e256596, 61c761fc21e00e45c33c2bb596be442d92fb8792 +2

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-g7fp-pvxq-ggj5

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ d56d938b4bef3e1421a42023cdcd6e13c1f50831, < abdc57c7ebabaaf0b622178a6a85834e1e54ff80	Fixed in abdc57c7ebabaaf0b622178a6a85834e1e54ff80
LinuxLinux	Affected ≥ d56d938b4bef3e1421a42023cdcd6e13c1f50831, < a22fb44e988b01b82235ea07f0bf0fc73e256596	Fixed in a22fb44e988b01b82235ea07f0bf0fc73e256596
LinuxLinux	Affected ≥ d56d938b4bef3e1421a42023cdcd6e13c1f50831, < 61c761fc21e00e45c33c2bb596be442d92fb8792	Fixed in 61c761fc21e00e45c33c2bb596be442d92fb8792
LinuxLinux	Affected ≥ d56d938b4bef3e1421a42023cdcd6e13c1f50831, < 14f56e9c0b8fdc2e178acdbec9781e90ef46f7e9	Fixed in 14f56e9c0b8fdc2e178acdbec9781e90ef46f7e9
LinuxLinux	Affected ≥ d56d938b4bef3e1421a42023cdcd6e13c1f50831, < 2c75ebae8a7f09c99e31c7042b7d4d595f03b2b1	Fixed in 2c75ebae8a7f09c99e31c7042b7d4d595f03b2b1
LinuxLinux	Affected =5.12	Fixed in–

AI-suggested

No specific workaround or mitigation is provided in the available data.

Description

CVE-2026-99254 is a Linux kernel vulnerability in the io_uring subsystem where cancelling tasks can be flooded with repeated task_work callbacks. This occurs because the cancellation process queues callbacks repeatedly without removing nodes properly, causing a task to consume excessive CPU and work item resources. The issue can cause tasks to become stuck for minutes, including during execve() calls, without requiring any privileges.

Impact

Affected tasks can become stuck in a loop of repeated task_work callbacks, consuming CPU and work queue resources for minutes. This can delay task termination or execve() calls, potentially leading to denial of service conditions on the affected system. No privilege is required to trigger this behavior, increasing the risk of exploitation by unprivileged users.

Summary

The vulnerability in the Linux kernel's io_uring subsystem involves the io_ring_exit_work() function repeatedly queuing task_work callbacks to tasks that are cancelling. The io_tctx_exit_cb() callback does not remove nodes while the task is in io_uring_cancel_generic(), leading to continuous re-queuing of callbacks. This causes a task to run excessive callbacks, consuming CPU and work item resources, potentially for extended periods. The problem affects tasks exiting or executing new programs (execve()), causing them to be stuck in cancellation loops. No privilege is required to trigger this behavior. The root cause is that task_work_run() only returns when the list of nodes is empty, but the list never empties due to the callback re-queuing logic.

References

Community reviews

Loading reviews…