CVE-2026-74480
In the Linux kernel, the following vulnerability has been resolved:
net: bridge: stop fast-leave after deleting a port group
br_multicast_leave_group() iterates mp->ports with pp = &p->next in
its fast-leave path. After br_multicast_del_pg() removes p,
continuing the loop advances pp through the deleted entry.
If multicast-to-unicast was enabled, the bridge can hold multiple port
groups for the same port and group with different source MAC
addresses. Once multicast-to-unicast is disabled,
br_port_group_equal() matches those entries by port only. A fast leave
can then delete one entry and continue from its stale next pointer,
leaving mp->ports pointing at a deleted port group.
Fast leave only needs to remove one matching port group. Break after
br_multicast_del_pg() so the loop stops before dereferencing the
removed entry.
CSIRTS triage
- What
- The bridge fast-leave function continues processing after a port group is deleted, causing denial of service.
- Who is affected
- Networked systems using Linux bridge with multicast fast-leave enabled on affected kernel versions.
- Urgency
- High priority; DoS condition is achievable and affects network availability, CVSS 7.5.
- Action
- Apply kernel patch to stop fast-leave after port group deletion or update to a patched kernel version immediately.
AI-assisted analysis generated from the source advisory — verify against the original.
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Exploitation outlook
- Low exploitation risk0.53% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 42% of all EPSS-scored CVEs.
Advisory coverage (2)
External references
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