NAPI Scheduling Flaw in Linux Kernel's igb Driver by Intel

CVE-2026-31691

What is CVE-2026-31691?

A vulnerability exists in the igb driver of the Linux kernel, specifically due to improper handling of NAPI scheduling during abrupt termination of AF_XDP zero-copy applications. When such an application is killed unexpectedly, the XSK buffer pool is destroyed, yet NAPI polling continues, resulting in the igb_clean_rx_irq_zc() function failing to clear the NAPI state. This improper state management causes the igb_down() function to block indefinitely, leading to severe system stall where the TX watchdog may trigger, and the TX queue remains blocked. The vulnerability arises from the redundant use of napi_synchronize() before napi_disable(), which is unnecessary as napi_disable() already provides the necessary guarantees to properly handle polling state changes.

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