VulnerabilityPublished 3 Nov 2026

CVE-2026-99253: Linux kernel · io_uring/cancel: rearm local work wake up before sleep

Source GCVE Database

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Authoritative record:CVE-2026-99253· Medium

Not known to be exploited : upgrade to aaa06bb9fc03384f7cf2dbc3e43f2939cc7791b2 when convenient.

Data as of 3 Nov 2026, 13:28 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 aaa06bb9fc03384f7cf2dbc3e43f2939cc7791b2

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-c86r-6x5c-x35m

What to do

Upgrade Linux kernel to aaa06bb9fc03384f7cf2dbc3e43f2939cc7791b2.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ d46ab2c98ababa19b41a5709b6921d7b1add7f74, < aaa06bb9fc03384f7cf2dbc3e43f2939cc7791b2	Fixed in aaa06bb9fc03384f7cf2dbc3e43f2939cc7791b2
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 has been applied to the Linux kernel to rearm the wake-up count correctly after setting the task state and before checking the local work list. Users should update to the fixed kernel version once available.

Description

A vulnerability in the Linux kernel's io_uring subsystem involving improper handling of local work wake-up counts can cause tasks to become stuck in execution or exit states, waiting indefinitely until a signal wakes them. This issue arises from the timing of rearming the wake-up count relative to task state changes and local work queue processing.

Impact

Affected tasks in the Linux kernel using io_uring cancellation may become stuck indefinitely in a sleep state (TASK_INTERRUPTIBLE) waiting for a wake-up event that was lost due to timing issues. This can cause processes to hang, particularly those exiting or executing, potentially leading to system instability or denial of service conditions where tasks do not proceed as expected.

Summary

The vulnerability in the Linux kernel's io_uring cancel mechanism involves the handling of the ->cq_wait_nr counter used to wake cancelling tasks. io_uring_try_cancel_requests() sets this counter to 1 to ensure the cancelling task is woken by the next io_req_local_work_add() call. However, io_uring_cancel_generic() sets the task state to TASK_INTERRUPTIBLE later, and if the wake-up occurs while the task is running, it is lost. If the local work queue entry is delayed after queueing, the sleeping task can miss the wake-up and become stuck in schedule() until a signal arrives. The fix involves rearming the wake-up count after setting the task state and before checking the local work list to ensure the task is properly woken.

References

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