CVE-2026-23440 addresses a race condition in the Linux kernel's mlx5e network driver related to IPSec ESN update handling in full offload mode. When the device signals an ESN wrap event, the driver validates and processes this event by querying the IPSec ASO and modifying the kernel's xfrm state. During this process, the driver temporarily releases and re-acquires the xfrm state lock, creating a race condition if the event acknowledgment is not properly handled by setting the esn_event_arm field. This flaw could cause the driver to mishandle ESN updates, potentially leading to system instability or denial of service. The vulnerability affects multiple Linux kernel versions prior to 6.8.0-1064.72 and related builds. A patch is available and included in recent Linux kernel updates.

The vulnerability does not impact confidentiality or integrity but has an impact on availability, as exploitation could cause a denial of service by crashing or destabilizing the system. The CVSS v3.1 score is 7.5 (High) with vector AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H, indicating remote network attack with low complexity and no privileges or user interaction required. No known exploits are reported in the wild.

An official fix is available and included in Linux kernel updates for the affected versions. Users should apply the kernel updates provided by their Linux distribution (e.g., Ubuntu) and reboot their systems to ensure the vulnerability is remediated. Due to an ABI change in the kernel updates, recompilation and reinstallation of third-party kernel modules may be necessary. Follow vendor instructions for updating and rebuilding kernel modules as needed.