CVE-2026-31691 is a medium severity vulnerability in the Linux kernel's igb network driver. It involves improper handling of NAPI synchronization during abrupt termination of AF_XDP zero-copy applications, causing the TX queue to stall indefinitely. The issue arises because napi_synchronize() spins waiting for a state that never clears, leading to a deadlock in igb_down(). The fix removes the redundant napi_synchronize() call and reorders napi_disable() to ensure proper polling shutdown.