A flaw in the Linux kernel’s fbnic driver allows an attacker or misconfiguration to increase the MTU beyond the hardware fragmentation threshold after an XDP program has been attached. The driver will then drop all multi-fragment frames, effectively disabling new TCP streams and potentially causing a denial of service for applications relying on those streams. The vulnerability is rooted in missing input validation for MTU adjustments after attachment of XDP programs.

Linux kernel implementations that use the fbnic driver, especially when XDP programs are attached. The issue applies to all kernel releases prior to the patch that introduced MTU validation. No specific minor or major version ranges are listed, so any kernel variant containing the fbnic driver is potentially affected.

The CVSS score is not disclosed, and EPSS is not available, making it difficult to quantify exploitation probability. The vulnerability is not in the CISA KEV catalog. Attackers would need to influence MTU changes on a vulnerable system, a scenario more likely in a compromised or misconfigured environment. The risk remains high for deployments that use XDP on fbnic without ensuring MTU integrity, as packet drops could disrupt critical network services.