{"id":"CVE-2026-99117","title":"net: bridge: mcast: don't truncate the port group walk on teardown","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: bridge: mcast: don't truncate the port group walk on teardown\n\n__br_multicast_disable_port_ctx() and br_multicast_del_port() walk\nport->mglist with hlist_for_each_…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= b08123684bd55fa6d6ee4b52d4ae3040fadb5aa2 < 8243d587a081e790ad96e80d48eef44d9f7ef005","Linux >= b08123684bd55fa6d6ee4b52d4ae3040fadb5aa2 < b45e8c24608c992d1e2cea047eb5bcbfa537f86b","Linux >= b08123684bd55fa6d6ee4b52d4ae3040fadb5aa2 < 5a3f7a683aee56e1f15c9d53041f3236767eaae7","Linux 5.10"],"published":"2026-10-28","updated":"2026-10-28","sourceUpdated":"2026-10-28T10:34:33.874Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-99117","references":[{"url":"https://git.kernel.org/stable/c/8243d587a081e790ad96e80d48eef44d9f7ef005"},{"url":"https://git.kernel.org/stable/c/b45e8c24608c992d1e2cea047eb5bcbfa537f86b"},{"url":"https://git.kernel.org/stable/c/5a3f7a683aee56e1f15c9d53041f3236767eaae7"}],"tags":["cve.org"],"ingestedAt":"2026-10-28T11:09:40.449Z","slug":"CVE-2026-99117","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nnet: bridge: mcast: don't truncate the port group walk on teardown\n\n__br_multicast_disable_port_ctx() and br_multicast_del_port() walk\nport->mglist with hlist_for_each_entry_safe(). However,\nbr_multicast_find_del_pg() can also delete other entries from the same\nlist through br_multicast_fwd_src_remove() or __fwd_del_star_excl().\n\nIf such an entry is the iterator's saved next node, hlist_del_init()\nclears its ->next and terminates the walk early. The reproducer triggers\nthis in both teardown walks, leaving port groups in the bridge mdb with\na dangling ->key.port after del_nbp() frees the port:\n\n  BUG: KASAN: slab-use-after-free in __mdb_fill_info+0x1191/0x1320\n   __mdb_fill_info+0x1191/0x1320\n   br_mdb_dump+0x594/0xe40\n   rtnl_mdb_dump+0x1cf/0x5d0\n\nUse hlist_del_init_rcu() to unlink the group while preserving ->next.\nbr_multicast_del_pg() and the teardown walks run under\nbr->multicast_lock. The GC worker must acquire the same lock before\ndetaching the group for destruction, so the node remains alive while\nthe walk uses the preserved pointer.\n\nPreserving ->next means a walk can now reach a group that an earlier\niteration already deleted as a side effect. That group is off mp->ports,\nso br_multicast_find_del_pg() would fall through its port scan and hit\nthe trailing WARN_ON(1). Skip such groups at the top of that helper: a\nport group is put on port->mglist when it is created and only unlinked\nwhen it is deleted, so hlist_unhashed() identifies exactly this case.\n\n## Affected\n\n- `Linux >= b08123684bd55fa6d6ee4b52d4ae3040fadb5aa2 < 8243d587a081e790ad96e80d48eef44d9f7ef005`\n- `Linux >= b08123684bd55fa6d6ee4b52d4ae3040fadb5aa2 < b45e8c24608c992d1e2cea047eb5bcbfa537f86b`\n- `Linux >= b08123684bd55fa6d6ee4b52d4ae3040fadb5aa2 < 5a3f7a683aee56e1f15c9d53041f3236767eaae7`\n- `Linux 5.10`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}