The Linux kernel contains a use‑after‑free flaw in the macvlan subsystem. When a macvlan interface is created in SOURCE mode with the MACADDR_ADD or MACADDR_SET option, and the underlying register_netdevice() call fails (for example, due to an invalid link name), the kernel incorrectly leaves a reference to the freed net_device in a hash table. Subsequent packets routed through the macvlan port with a matching source MAC address trigger a use‑after‑free in macvlan_forward_source(), which can crash the kernel. The CVSS score of 7.8 classifies the flaw as high severity.

All Linux kernels are affected, from version 4.9 through at least 6.19‑rc8, as indicated by the CPE list. The vulnerability is present in the mainline kernel, so any distribution that has not yet released a patched kernel version will be vulnerable. The flaw applies to any system that can create macvlan interfaces in SOURCE mode, which typically requires root or equivalent privileges.

The likelihood of exploitation is low, with an EPSS score of less than 1%, and the vulnerability is not listed in CISA’s Known Exploited Vulnerabilities catalog. An attacker would need the ability to create macvlan interfaces and send traffic that triggers the use‑after‑free, implying a privileged local attack. No publicly available exploit code has been reported, but a kernel panic can be reproduced with a simple script, indicating that exploitation could be achieved with moderate skill and the appropriate permissions.