VulnerabilityPublished 3 Nov 2026

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

Affects Linux kernelSource CVE Database V5

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

Data as of 3 Nov 2026, 11:46 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.

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

This vulnerability is fixed in the Linux kernel commits identified by hashes abdc57c7ebabaaf0b622178a6a85834e1e54ff80, a22fb44e988b01b82235ea07f0bf0fc73e256596, 61c761fc21e00e45c33c2bb596be442d92fb8792, 14f56e9c0b8fdc2e178acdbec9781e90ef46f7e9, and 2c75ebae8a7f09c99e31c7042b7d4d595f03b2b1. Users should upgrade to a Linux kernel version including these fixes. No other mitigation is indicated by the vendor advisory.

Description

A vulnerability in the Linux kernel's io_uring subsystem causes a cancelling task to be flooded with repeated task_work callbacks, leading to excessive CPU usage and potential task hang. This occurs because the cancellation process repeatedly queues callbacks without removing nodes properly, causing a task to remain busy for extended periods. No privilege is required to trigger this behavior. The issue is fixed in later kernel versions.

Impact

A cancelling or exiting task in the Linux kernel can become stuck in a loop of repeated task_work callbacks, consuming CPU resources excessively and potentially hanging for minutes. This can degrade system performance and affect task termination. No privilege is required to trigger this condition, making it a denial-of-service risk on affected systems.

Summary

The Linux kernel's io_uring subsystem had a flaw where io_ring_exit_work() repeatedly asked tasks to remove their tctx nodes via task_work callbacks. However, io_tctx_exit_cb() does not modify the node during io_uring_cancel_generic(), which removes all nodes at its end. This caused the work item to re-queue the callback immediately after completion, leading to a flood of callbacks to a single cancelling task. The task_work_run() function only returns when the list is empty, but due to this behavior, the list never empties, causing the task to consume CPU indefinitely and potentially hang for minutes. This affects tasks exiting or executing execve(), with no privilege required. The issue is resolved in fixed Linux kernel commits.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 3 Nov 2026, 11:46 UTC

Technical details

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