CVE-2026-31691

A flaw was found in the Linux kernel's igb network driver. When an AF_XDP zero-copy application terminates abruptly, the network driver's NAPI polling mechanism can become stuck. This prevents the igb_down() function from completing, leading to the TX queue becoming permanently stalled. This can result in a Denial of Service (DoS) condition, making the network interface unresponsive.

igb can hang in igb_down when an AF_XDP zero copy application terminates abruptly and the XSK buffer pool is destroyed while NAPI polling keeps running. In this state the zero copy RX poll path can keep returning a full budget which prevents napi_complete_done from clearing NAPI_STATE_SCHED. igb_down then calls napi_synchronize and waits indefinitely for NAPI_STATE_SCHED to clear which never happens. This blocks the down path, triggers the TX watchdog, and can leave the TX queue permanently stalled which is a denial of service for the affected network device. The issue is not network reachable and requires local control of the host to set up and exercise AF_XDP zero copy.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

To mitigate this issue, prevent module igb from being loaded. Please see https://access.redhat.com/solutions/41278 for how to blacklist a kernel module to prevent it from loading automatically.