The Linux kernel’s fbnic driver lacks validation for MTU adjustments after an XDP program is attached. When the MTU is increased beyond the hardware fragmentation threshold, packets are fragmented across multiple buffers and any attached XDP program in single‑buffer mode will drop those multi‑frag frames. This results in dropped packets that can prevent the establishment of new TCP streams, effectively causing a denial of service for network applications relying on XDP.

All Linux kernel variants that include the fbnic network driver are affected, particularly systems that have XDP programs attached to fbnic interfaces. The vulnerability applies to every kernel release before the patch that added MTU validation; no specific version ranges are listed, so any kernel pointing to the fbnic module is potentially vulnerable.

The CVSS score of 5.5 denotes moderate severity, and the EPSS score of less than 1% indicates a low likelihood of exploitation. The vulnerability is not listed in the CISA KEV catalog. Based on the description, it is inferred that attackers would need to influence MTU changes on a vulnerable system, as increasing the MTU after XDP attachment triggers the issue. This scenario is more likely in a compromised or misconfigured environment. The likely attack vector involves manipulating system configuration to raise the MTU beyond the hardware fragmentation threshold, leading to packet drops and potential denial of service.