Linux Kernel up to 6.17.2 thunderbolt cancel_delayed_work use after free

Summaryinfo

A vulnerability was found in Linux Kernel up to 6.17.2 and classified as critical. This affects the function cancel_delayed_work of the component thunderbolt. Such manipulation leads to use after free. This vulnerability is listed as CVE-2025-40002. There is no available exploit. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability was found in Linux Kernel up to 6.17.2 and classified as critical. Affected by this issue is the function cancel_delayed_work of the component thunderbolt. The manipulation with an unknown input leads to a use after free vulnerability. Using CWE to declare the problem leads to CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. Impacted is confidentiality, integrity, and availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: thunderbolt: Fix use-after-free in tb_dp_dprx_work The original code relies on cancel_delayed_work() in tb_dp_dprx_stop(), which does not ensure that the delayed work item tunnel->dprx_work has fully completed if it was already running. This leads to use-after-free scenarios where tb_tunnel is deallocated by tb_tunnel_put(), while tunnel->dprx_work remains active and attempts to dereference tb_tunnel in tb_dp_dprx_work(). A typical race condition is illustrated below: CPU 0 | CPU 1 tb_dp_tunnel_active() | tb_deactivate_and_free_tunnel()| tb_dp_dprx_start() tb_tunnel_deactivate() | queue_delayed_work() tb_dp_activate() | tb_dp_dprx_stop() | tb_dp_dprx_work() //delayed worker cancel_delayed_work() | tb_tunnel_put(tunnel); | | tunnel = container_of(...); //UAF | tunnel-> //UAF Replacing cancel_delayed_work() with cancel_delayed_work_sync() is not feasible as it would introduce a deadlock: both tb_dp_dprx_work() and the cleanup path acquire tb->lock, and cancel_delayed_work_sync() would wait indefinitely for the work item that cannot proceed. Instead, implement proper reference counting: - If cancel_delayed_work() returns true (work is pending), we release the reference in the stop function. - If it returns false (work is executing or already completed), the reference is released in delayed work function itself. This ensures the tb_tunnel remains valid during work item execution while preventing memory leaks. This bug was found by static analysis.

The advisory is available at git.kernel.org. This vulnerability is handled as CVE-2025-40002 since 04/16/2025. The exploitation is known to be easy. Technical details are known, but there is no available exploit. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 02/13/2026).

The vulnerability scanner Nessus provides a plugin with the ID 271678 (Linux Distros Unpatched Vulnerability : CVE-2025-40002), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.17.3 or 6.18-rc1 eliminates this vulnerability. Applying the patch c07923f6a8729fc27ee652221a51702ff6654097/67600ccfc4f38ebd331b9332ac94717bfbc87ea7 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 (271678), EUVD (EUVD-2025-34987) and CERT Bund (WID-SEC-2025-2340). If you want to get best quality of vulnerability data, you may have to visit VulDB.

Affected

• Debian Linux
• Amazon Linux 2
• Ubuntu Linux
• SUSE Linux
• Oracle Linux
• SUSE openSUSE
• Open Source Linux Kernel

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.17.0
• 6.17.1
• 6.17.2

License

• open-source

Website

• Vendor: https://www.kernel.org/

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Entryinfo

If you want to get best quality of vulnerability data, you may have to visit VulDB.

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