CVE-2026-23440

In the Linux kernel, the following vulnerability has been resolved:

net/mlx5e: Fix race condition during IPSec ESN update

In IPSec full offload mode, the device reports an ESN (Extended

Sequence Number) wrap event to the driver. The driver validates this

event by querying the IPSec ASO and checking that the esn_event_arm

field is 0x0, which indicates an event has occurred. After handling

the event, the driver must re-arm the context by setting esn_event_arm

back to 0x1.

A race condition exists in this handling path. After validating the

event, the driver calls mlx5_accel_esp_modify_xfrm() to update the

kernel's xfrm state. This function temporarily releases and

re-acquires the xfrm state lock.

So, need to acknowledge the event first by setting esn_event_arm to

0x1. This prevents the driver from reprocessing the same ESN update if

the hardware sends events for other reason. Since the next ESN update

only occurs after nearly 2^31 packets are received, there's no risk of

missing an update, as it will happen long after this handling has

finished.

Processing the event twice causes the ESN high-order bits (esn_msb) to

be incremented incorrectly. The driver then programs the hardware with

this invalid ESN state, which leads to anti-replay failures and a

complete halt of IPSec traffic.

Fix this by re-arming the ESN event immediately after it is validated,

before calling mlx5_accel_esp_modify_xfrm(). This ensures that any

spurious, duplicate events are correctly ignored, closing the race

window.