CVE-2026-72421

A flaw was found in the Linux kernel. When the CONFIG_IP_MULTIPLE_TABLES option is enabled without additional routing rules, the fib_lookup() function can incorrectly process error routes. This allows an error route in the local or main routing tables to be overwritten by a default route. The consequence is inconsistent network behavior, potentially leading to a denial of service for affected network paths.

This vulnerability is rated as Low severity because exploitation requires local administrative network capabilities to manipulate routing tables, and the resulting impact is limited to incorrect path resolution rather than kernel panics or data leakage. In default Red Hat Enterprise Linux deployments, network setups typically configure explicit routing rules or rely on standard tables where this specific error route override does not occur during normal operations. Unprivileged users cannot configure or manipulate routing tables to trigger this behavior without elevated privileges.

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.