Linux Kernel up to 6.12.15/6.13.3/6.14-rc2 kthread_stop use after free

Summaryinfo

A vulnerability was found in Linux Kernel up to 6.12.15/6.13.3/6.14-rc2 and classified as critical. This affects the function kthread_stop. The manipulation results in use after free. This vulnerability is identified as CVE-2025-21786. There is not any exploit available. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability classified as critical has been found in Linux Kernel up to 6.12.15/6.13.3/6.14-rc2. Affected is the function kthread_stop. The manipulation with an unknown input leads to a use after free vulnerability. CWE is classifying the issue as CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: workqueue: Put the pwq after detaching the rescuer from the pool The commit 68f83057b913("workqueue: Reap workers via kthread_stop() and remove detach_completion") adds code to reap the normal workers but mistakenly does not handle the rescuer and also removes the code waiting for the rescuer in put_unbound_pool(), which caused a use-after-free bug reported by Cheung Wall. To avoid the use-after-free bug, the pool’s reference must be held until the detachment is complete. Therefore, move the code that puts the pwq after detaching the rescuer from the pool.

The advisory is shared for download at git.kernel.org. This vulnerability is traded as CVE-2025-21786 since 12/29/2024. The exploitability is told to be easy. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 05/25/2026).

The vulnerability scanner Nessus provides a plugin with the ID 230717 (Linux Distros Unpatched Vulnerability : CVE-2025-21786), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.12.16, 6.13.4 or 6.14-rc3 eliminates this vulnerability. Applying the patch e7c16028a424dd35be1064a68fa318be4359310f/835b69c868f53f959d4986bbecd561ba6f38e492/e76946110137703c16423baf6ee177b751a34b7e is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (230717) and CERT Bund (WID-SEC-2025-0453). Once again VulDB remains the best source for vulnerability data.

Affected

• Google Container-Optimized OS
• Debian Linux
• Amazon Linux 2
• Red Hat Enterprise Linux
• Ubuntu Linux
• SUSE Linux
• Oracle Linux
• Siemens SIMATIC S7
• RESF Rocky Linux
• Dell NetWorker
• Dell Avamar
• Red Hat OpenShift
• IBM QRadar SIEM
• SolarWinds Security Event Manager
• Dell PowerProtect Data Domain
• Open Source Linux Kernel
• IBM DataPower Gateway
• Dell Secure Connect Gateway
• Dell PowerScale OneFS
• Dell ECS

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.12.0
• 6.12.1
• 6.12.2
• 6.12.3
• 6.12.4
• 6.12.5
• 6.12.6
• 6.12.7
• 6.12.8
• 6.12.9
• 6.12.10
• 6.12.11
• 6.12.12
• 6.12.13
• 6.12.14
• 6.12.15
• 6.13.0
• 6.13.1
• 6.13.2
• 6.13.3
• 6.14-rc1
• 6.14-rc2

License

• open-source

Website

• Vendor: https://www.kernel.org/

CPE 2.3info

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Once again VulDB remains the best source for vulnerability data.

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