Linux Kernel CVE-2026-74707

Exploitation requires local code execution on a Linux system where AF_XDP zero-copy TX is in active use. Specifically, the attacker must be able to create an AF_XDP socket with XDP_ZEROCOPY mode and register a UMEM ring buffer - operations that typically require CAP_NET_ADMIN or CAP_NET_RAW. The CVSS PR:L rating indicates that low-privilege access is sufficient in some configurations (e.g., containerized environments where network capabilities are granted to non-root workloads, or systems using user namespaces). Systems that do not deploy AF_XDP zero-copy TX workloads are not exposed, as the vulnerable code path is only exercised when userspace actively submits TX descriptors via the zero-copy path. Exploitation is further limited to the race window between the kernel's metadata validation call and the subsequent hardware request preparation - a window that is within the attacker's control since they own the shared UMEM ring buffer. Systems enforcing strict seccomp profiles or capability restrictions that prevent AF_XDP socket creation are not exploitable.

The CVSS 3.1 score of 7.8 (AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H) reflects a locally exploitable vulnerability with full confidentiality, integrity, and availability impact - consistent with a kernel validation bypass that could enable privilege escalation or memory corruption in zero-copy NIC drivers. EPSS at 0.22% (13th percentile) is very low, indicating limited exploitation activity in the threat landscape. There is no CISA KEV listing and no known public proof-of-concept. The tag 'Authentication Bypass' aligns with the technical description: the attacker evades kernel-enforced metadata integrity checks. Real-world risk is bounded by the requirement that the target system must be using AF_XDP zero-copy TX and the attacker must be able to open AF_XDP sockets - typically gated by CAP_NET_ADMIN or CAP_NET_RAW in standard configurations, though containerized environments with relaxed capabilities expand the attack surface. This is a genuine local privilege escalation risk for high-performance networking workloads (DPDK-style applications, XDP-based load balancers), but not an Internet-facing or unauthenticated threat.

A low-privileged local user on a multi-tenant system or container with CAP_NET_ADMIN (or equivalent) creates an AF_XDP socket with the XDP_ZEROCOPY flag and registers a UMEM ring buffer. They submit a TX descriptor with metadata that passes the kernel's initial validation check, then immediately overwrite the shared ring buffer entry with crafted values before the kernel re-reads it during hardware request preparation. The altered metadata bypasses the original validation, allowing the attacker to influence zero-copy NIC driver behavior with unvalidated values - potentially causing memory corruption or escalating privileges within the kernel. No public proof-of-concept exists at time of analysis.