VulnerabilityPublished 3 Nov 2026Updated 4 Nov 2026

CVE-2026-99255: Linux kernel · io_uring/io-wq: don't hide a link from cancellations

Affects Linux kernelSource GCVE Database

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Authoritative record:CVE-2026-99255· Medium

Not known to be exploited.

Data as of 5 Nov 2026, 00:01 UTC

Severity

Medium

Rated by Threat Radar · CVSS not yet scored by NVD

Thin evidence

One scorer or none

EPSS: 0.1% chance of exploitation in 30 days – higher than 9% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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 4 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

Affected software

Product	Affected	Fixed in
Ubuntu 26.10linux`pkg:deb/ubuntu/linux?arch=source&distro=stonking`Other threats	Affected 7.0.0-14.14 – 7.3.0-10.10 7 affected builds	Fixed in–
Ubuntu 26.10linux-aws`pkg:deb/ubuntu/linux-aws?arch=source&distro=stonking`Other threats	Affected 7.0.0-1004.4 – 7.3.0-1004.4 6 affected builds	Fixed in–
Ubuntu 26.10linux-azure`pkg:deb/ubuntu/linux-azure?arch=source&distro=stonking`Other threats	Affected 7.0.0-1004.4 – 7.3.0-1004.4 6 affected builds	Fixed in–
Ubuntu 26.10linux-azure-fde`pkg:deb/ubuntu/linux-azure-fde?arch=source&distro=stonking`Other threats	Affected 7.0.0-1004.4 – 7.3.0-1004.5 4 affected builds	Fixed in–
Ubuntu 26.10linux-gcp`pkg:deb/ubuntu/linux-gcp?arch=source&distro=stonking`Other threats	Affected 7.0.0-1003.3 – 7.3.0-1004.4 6 affected builds	Fixed in–
Ubuntu 26.10linux-oracle`pkg:deb/ubuntu/linux-oracle?arch=source&distro=stonking`Other threats	Affected 7.0.0-1003.3 – 7.3.0-1004.4 6 affected builds	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 tightens task exit cancellations to handle linked requests correctly, ensuring they are freed once they become the current work or are pending. Users should apply the updated Linux kernel versions that include this fix. No additional mitigation steps are indicated by the vendor advisory.

Description

CVE-2026-99255 is a vulnerability in the Linux kernel's io_uring subsystem related to the handling of linked requests during task exit cancellations. A timing window exists where a linked request is neither pending, current, nor parked, causing the exiting task to miss the request and go to sleep indefinitely. This can lead to a hang where the process cannot be killed, affecting system stability under certain workloads.

Impact

The vulnerability can cause processes to hang during exit, making them unkillable and potentially impacting system stability. This occurs under specific timing conditions when linked io_uring requests are cancelled during task exit. The impact is limited to scenarios involving linked asynchronous I/O requests and task/thread exit, with observed hangs occurring rarely under test conditions.

Summary

This vulnerability affects the Linux kernel's io_uring/io-wq subsystem. When a task exits, it cancels its tracked requests and waits for their completion. However, due to a timing gap during the freeing of linked requests, the cancellation function may not find the linked request, causing the task to sleep indefinitely. The worker continues processing the linked request, but since it is not completed or freed, no wake-up occurs, potentially causing the exiting process to hang and become unkillable. The issue is addressed by tightening task exit cancellations to ensure the linked request is found and freed properly, preventing the hang.

GCVE source: db.gcve.eu
OSV ID: UBUNTU-CVE-2026-99255
Osv Schema Version: 1.7.0
Ecosystems: Ubuntu:16.04:LTS, Ubuntu:18.04:LTS, Ubuntu:20.04:LTS, Ubuntu:Pro:20.04:LTS, Ubuntu:22.04:LTS, Ubuntu:Nvidia-BlueField:22.04:LTS, Ubuntu:Pro:Realtime:22.04:LTS, Ubuntu:Pro:FIPS-preview:22.04:LTS, Ubuntu:Pro:FIPS-updates:22.04:LTS, Ubuntu:24.04:LTS, Ubuntu:Nvidia-BlueField:24.04:LTS, Ubuntu:Pro:Realtime:24.04:LTS, Ubuntu:Pro:FIPS-updates:24.04:LTS, Ubuntu:26.10, Ubuntu:26.04:LTS

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 4 Nov 2026, 21:17 UTC

Technical details

References

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