A memory leak occurs when an HSR master device propagates VLAN 0 to its slave ports and later a slave device is unregistered while the HSR link remains active. The hsr_del_port routine fails to delete the VLAN identifiers that were synced to the slave, leaving a lingering reference count on VID 0. When the slave device is destroyed, its vlan_info structure remains allocated, causing unbounded kernel memory consumption over time.

Linux kernel implementations that include the HSR (High‑speed replication) feature, regardless of distribution, are susceptible. The issue exists in kernel versions prior to the commit that introduced vlan_vids_del_by_dev in hsr_del_port. Users with HSR configured on any kernel version before the patch are affected.

The CVSS score of 5.5 indicates moderate severity, with an EPSS of less than 1% suggesting a low likelihood of exploitation. However, the flaw can be triggered locally by repeatedly registering and unregistering HSR slave interfaces, such as during network namespace cleanup or interface destruction. Over time this can exhaust VM or host memory, leading to kernel instability or a denial‑of‑service condition. The attack vector is entirely local; an attacker would need access to configure or manage network interfaces on the target system.