CVE-2026-80733
Low risk· EPSS 11%Exploitation Probability (EPSS)
Low risk11th percentile - higher than 11% of all known CVEs
Summary
In the Linux kernel, the sk_mc_loop() function triggers WARN_ON_ONCE(1) for sockets that are neither AF_INET nor AF_INET6, e.g., AF_PACKET sockets when sending packets via raw/packet socket over virtual devices such as VRF or ipvlan. Non-INET sockets do not support IP_MULTICAST_LOOP or IPV6_MULTICAST_LOOP options, so loopback should default to true without generating a warning. The fix removes this warning.
Risk Assessment
The vulnerability causes unnecessary kernel log warnings, which may hinder detection of real issues. It does not pose a direct security threat but can be annoying in production environments.
Recommendation
Apply a Linux kernel update containing the fix that removes WARN_ON_ONCE() from sk_mc_loop().
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: net: remove WARN_ON_ONCE() from sk_mc_loop() sk_mc_loop() can be called for sockets that are neither AF_INET nor AF_INET6 (e.g. AF_PACKET sockets when sending packets via raw/packet socket over virtual devices such as VRF or ipvlan). In such cases, sk_family is not AF_INET/AF_INET6 and sk_mc_loop() falls through the switch statement and triggers WARN_ON_ONCE(1). Non-INET sockets do not support IP_MULTICAST_LOOP or IPV6_MULTICAST_LOOP options, so loopback should default to true without generating a warning.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS

