CVE-2026-80733: net: remove WARN_ON_ONCE() from sk_mc_loop()
In the Linux kernel, the following vulnerability has been resolved:
net: remove WARNONONCE() from skmcloop()
skmcloop() can be called for sockets that are neither AFINET nor AFINET6 (e.g. AFPACKET sockets when sending packets via raw/packet socket over virtual devices such as VRF or ipvlan).
In such cases, skfamily is not AFINET/AFINET6 and skmcloop() falls through the switch statement and triggers WARNONONCE(1).
Non-INET sockets do not support IPMULTICASTLOOP or IPV6MULTICASTLOOP options, so loopback should default to true without generating a warning.
Affected Software
Event History
Frequently Asked Questions
Which deployments are exposed to the warning condition?
The condition can affect Linux kernel systems where non-INET sockets, such as AF_PACKET sockets, send packets over virtual devices including VRF or ipvlan.
What is required to trigger the issue?
A socket whose family is neither AF_INET nor AF_INET6 must reach sk_mc_loop(). In the described example, this occurs when sending through a raw or packet socket over a virtual device.
What behavior occurs for affected non-INET sockets?
The function falls through its socket-family switch and triggers WARN_ON_ONCE(1). Non-INET sockets do not support IP_MULTICAST_LOOP or IPV6_MULTICAST_LOOP, and their loopback behavior should instead default to true without a warning.