Linux Kernel up to 7.2.13 io-wq io_uring_cancel_generic cur_work race condition

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5.3	$0-$5k	0.00

Summaryinfo

A vulnerability marked as critical has been reported in Linux Kernel up to 6.1.190/6.6.160/6.12.114/6.18.59/7.2.13. Affected is the function io_uring_cancel_generic of the component io-wq. This manipulation of the argument cur_work causes race condition. This vulnerability is handled as CVE-2026-99255. It is possible to launch the attack on the local host. There is not any exploit available. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability has been found in Linux Kernel up to 6.1.190/6.6.160/6.12.114/6.18.59/7.2.13 and classified as critical. Affected by this vulnerability is the function io_uring_cancel_generic of the component io-wq. The manipulation of the argument cur_work with an unknown input leads to a race condition vulnerability. The CWE definition for the vulnerability is CWE-362. The product contains a code sequence that can run concurrently with other code, and the code sequence requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence that is operating concurrently. As an impact it is known to affect availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: io_uring/io-wq: don't hide a link from cancellations A task that exits cancels its tracked requests and waits until they are gone. io_uring_cancel_generic() looks everywhere a request can be, and goes to sleep if it found nothing to cancel. It is woken up each time one of the requests of the task is completed by task work or freed. When io-wq is done with a request that has a link, there is a time in which the next request of the link can't be found: io_worker_handle_work() io_assign_current_work(worker, NULL) io_wq_free_work(work) io_req_find_next() // takes the link off the request io_free_req() // task work for the task io_assign_current_work(worker, linked) io_run_task_work() cond_resched() worker->cur_work = linked It is not pending, it is not the current work of a worker, and it is not yet on the list that it is about to be parked on. If the pass that the exiting task makes because of io_free_req() falls into that time, it finds nothing and the task goes to sleep. The worker then runs the link, which IO_WQ_BIT_EXIT doesn't prevent for bounded work. If that parks the request nothing is completed or freed, and nobody wakes up the task. If it is the process that exits it can't be killed any more either. NOP, IOSQE_ASYNC | IOSQE_IO_LINK FUTEX_WAIT, FUTEX2_PRIVATE exit of the thread, or of the process, up to 63us later With four of these per round 5 to 8 of 10,000 rounds hang (4 CPUs, KVM): io_uring_cancel_generic do_exit Commit f8b632e89a10 ("io_uring: tighten task exit cancellations") is about the same gap, and makes the task look again for whatever happens before io_free_req(). Free the request once the link is the current work of the worker, or pending. Whoever is woken up by that can find the link, until it is parked where cancellations look as well. To do so split io_wq_free_work() in two.

It is possible to read the advisory at git.kernel.org. This vulnerability is known as CVE-2026-99255 since 09/25/2026. The exploitation appears to be easy. Attacking locally is a requirement. Technical details of the vulnerability are known, but there is no available exploit.

The vulnerability scanner Nessus provides a plugin with the ID 375597 (Linux Distros Unpatched Vulnerability : CVE-2026-99255), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.1.191, 6.6.161, 6.12.115, 6.18.60 or 7.2.14 eliminates this vulnerability. Applying the patch 98470f164286f7f62aaee519d4d11b9370ce6d7b/d39ebc7a583d650b1d6da9b45e2ce96ad4d877e4/ebe8e97fb99d9f374c482902a00677cfd24a6c27/3e02b8df0e9fa1423ac2a4e03409a9329c30ac49/92e20e9c72bdf6cfa6f84eded7b33399bc7061da is able to eliminate this problem. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at Tenable (375597). Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.1.190
• 6.6.160
• 6.12.114
• 6.18.0
• 6.18.1
• 6.18.2
• 6.18.3
• 6.18.4
• 6.18.5
• 6.18.6
• 6.18.7
• 6.18.8
• 6.18.9
• 6.18.10
• 6.18.11
• 6.18.12
• 6.18.13
• 6.18.14
• 6.18.15
• 6.18.16
• 6.18.17
• 6.18.18
• 6.18.19
• 6.18.20
• 6.18.21
• 6.18.22
• 6.18.23
• 6.18.24
• 6.18.25
• 6.18.26
• 6.18.27
• 6.18.28
• 6.18.29
• 6.18.30
• 6.18.31
• 6.18.32
• 6.18.33
• 6.18.34
• 6.18.35
• 6.18.36
• 6.18.37
• 6.18.38
• 6.18.39
• 6.18.40
• 6.18.41
• 6.18.42
• 6.18.43
• 6.18.44
• 6.18.45
• 6.18.46
• 6.18.47
• 6.18.48
• 6.18.49
• 6.18.50
• 6.18.51
• 6.18.52
• 6.18.53
• 6.18.54
• 6.18.55
• 6.18.56
• 6.18.57
• 6.18.58
• 6.18.59
• 7.2.0
• 7.2.1
• 7.2.2
• 7.2.3
• 7.2.4
• 7.2.5
• 7.2.6
• 7.2.7
• 7.2.8
• 7.2.9
• 7.2.10
• 7.2.11
• 7.2.12
• 7.2.13

License

• open-source

Website

• Vendor: https://www.kernel.org/

CPE 2.3info

• 🔒
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CPE 2.2info

• 🔒
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CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 5.5
VulDB Meta Temp Score: 5.3

VulDB Base Score: 5.5
VulDB Temp Score: 5.3
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AV	AC	Au	C	I	A
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳

Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Race condition
CWE: CWE-362
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: No

Availability: 🔒
Status: Not defined
Price Prediction: 🔍
Current Price Estimation: 🔒

0-Day	Unlock	Unlock	Unlock	Unlock
Today	Unlock	Unlock	Unlock	Unlock

Nessus ID: 375597
Nessus Name: Linux Distros Unpatched Vulnerability : CVE-2026-99255

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 6.1.191/6.6.161/6.12.115/6.18.60/7.2.14
Patch: 98470f164286f7f62aaee519d4d11b9370ce6d7b/d39ebc7a583d650b1d6da9b45e2ce96ad4d877e4/ebe8e97fb99d9f374c482902a00677cfd24a6c27/3e02b8df0e9fa1423ac2a4e03409a9329c30ac49/92e20e9c72bdf6cfa6f84eded7b33399bc7061da

Timelineinfo

09/25/2026 CVE reserved
11/03/2026 +39 days Advisory disclosed
11/03/2026 +0 days VulDB entry created
11/04/2026 +1 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CNA: Linux
CVE: CVE-2026-99255 (🔒)

GCVE (CVE): GCVE-0-2026-99255
GCVE (VulDB): GCVE-100-430231

Entryinfo

Created: 11/03/2026 12:42
Updated: 11/04/2026 06:22
Changes: 11/03/2026 12:42 (60), 11/04/2026 06:22 (2)
Complete: 🔍
Cache ID: 216::103

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