CVE-2026-74709 describes a Linux kernel vulnerability in the xsk (AF_XDP) subsystem where user space can modify metadata flags after the kernel has processed a request. This can cause the kernel to write a timestamp even when none was requested by the packet submission. The vulnerability arises because the kernel rereads metadata flags during completion, leading to unintended timestamp writes. The patch clears the metadata pointer during request processing unless timestamp completion is explicitly requested, ensuring that completion handling uses the pointer directly rather than rereading flags. The fix accounts for multi-packet WQE paths by resetting pointers per batch and ensures other zero-copy and generic paths reset pointers per descriptor, preventing the issue.

The vulnerability could cause the kernel to write timestamps for packets that did not request them, potentially leading to incorrect metadata being recorded. There is no indication of direct privilege escalation or arbitrary code execution. The impact is limited to incorrect timestamp metadata handling in the kernel's xsk subsystem.

A fix for this vulnerability has been implemented in the Linux kernel by clearing the metadata pointer during request processing unless timestamp completion is requested. Users should update to the patched Linux kernel version that includes this fix. Since no patch links or specific versions are provided, users should consult the official Linux kernel advisories or their distribution's security updates for the relevant patch.