Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition') in Linux kernel - CVE-2026-23393

Detailed vulnerability description

The vulnerability allows a local user to cause a denial of service.

The vulnerability exists due to a race condition in the bridge CFM component when handling peer MEP deletion. A local user can trigger the deletion of a peer MEP, leading to a use-after-free condition if a delayed work item is rescheduled after cancellation but before memory is freed, resulting in a system crash.

The race condition occurs because br_cfm_frame_rx() runs in softirq context under RCU read lock and can re-schedule the delayed work between the cancellation and the memory release.

How to mitigate CVE-2026-23393

Sources

• https://git.kernel.org/stable/c/1fd81151f65927fd9edb8ecd12ad45527dbbe5ab
• https://git.kernel.org/stable/c/3715a00855316066cdda69d43648336367422127
• https://git.kernel.org/stable/c/d8f35767bacb3c7769d470a41cf161e3f3c07e70
• https://git.kernel.org/stable/c/e89dbd2736a45f0507949af4748cbbf3ff793146