{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-99117","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2026-09-25T10:25:14.392Z","datePublished":"2026-10-28T10:34:33.874Z","dateUpdated":"2026-10-31T12:43:18.238Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-10-31T12:43:18.238Z"},"descriptions":[{"lang":"en","value":"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_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."}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - A local RTM_SETLINK with IFLA_MASTER=0 reaches rtnl_setlink()→do_set_master()→br_del_if()→del_nbp()→br_multicast_del_port()→br_multicast_find_del_pg()→patched br_multicast_del_pg(); IGMPv3 reports can prepare membership state but cannot perform the required port teardown.\nAC:L - By adding several temporary (S,G) entries before corresponding IGMPv3 MODE_IS_INCLUDE reports, the attacker deterministically orders port->mglist so cascading deletion removes each saved next node; detaching the port then triggers both truncated walks without a race or external timing.\nPR:L - rtnetlink_rcv_msg() requires CAP_NET_ADMIN in the socket's network namespace for RTM_NEWMDB and RTM_SETLINK. set_cred_user_ns() grants that capability to an unprivileged caller in a new user and network namespace, so ordinary local access suffices.\nUI:N - The attacker creates the bridge and memberships, injects the IGMPv3 reports, detaches the port, and requests RTM_GETMDB without requiring another user to act.\nS:U - The dangling net_bridge_port pointer and surviving bridge MDB groups remain within the host kernel's security authority; exploitation from a user-created network namespace is ordinary kernel privilege escalation, not a VM, IOMMU, or hypervisor boundary crossing.\nC:H - The surviving port group retains pg->key.port after release_nbp() frees the net_bridge_port; RTM_GETMDB reaches __mdb_fill_info(), which follows reclaimed port->dev and returns derived data, allowing heap reclamation to steer kernel reads through the dangling pointer.\nI:H - When a surviving source expires, br_multicast_group_src_expired() reaches br_multicast_del_pg() through the dangling key.port; br_multicast_port_ngroups_dec() then writes mdb_n_entries through freed or reclaimed port memory, supporting memory corruption and control-flow exploitation.\nA:H - The demonstrated RTM_GETMDB path produces a KASAN slab-use-after-free in __mdb_fill_info(), while surviving source or port-group timers also dereference the freed port; these paths can oops or panic the kernel and are repeatable from the attacker's namespace."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/bridge/br_multicast.c"],"versions":[{"version":"b08123684bd55fa6d6ee4b52d4ae3040fadb5aa2","lessThan":"be331b23c650de9518f8266b901d8abb9b36af77","status":"affected","versionType":"git"},{"version":"b08123684bd55fa6d6ee4b52d4ae3040fadb5aa2","lessThan":"ab836d56ff43f2e7927e88c83cd02c47a98a672e","status":"affected","versionType":"git"},{"version":"b08123684bd55fa6d6ee4b52d4ae3040fadb5aa2","lessThan":"025c25ad73323c7dc5af4ee97fe0a2c0b3c177c8","status":"affected","versionType":"git"},{"version":"b08123684bd55fa6d6ee4b52d4ae3040fadb5aa2","lessThan":"b0db9f4ff402becff710ab27dbd9f6fe4850b47e","status":"affected","versionType":"git"},{"version":"b08123684bd55fa6d6ee4b52d4ae3040fadb5aa2","lessThan":"e69d4927dacd6ddaff09777a89efc0d3143d3b0d","status":"affected","versionType":"git"},{"version":"b08123684bd55fa6d6ee4b52d4ae3040fadb5aa2","lessThan":"8243d587a081e790ad96e80d48eef44d9f7ef005","status":"affected","versionType":"git"},{"version":"b08123684bd55fa6d6ee4b52d4ae3040fadb5aa2","lessThan":"b45e8c24608c992d1e2cea047eb5bcbfa537f86b","status":"affected","versionType":"git"},{"version":"b08123684bd55fa6d6ee4b52d4ae3040fadb5aa2","lessThan":"5a3f7a683aee56e1f15c9d53041f3236767eaae7","status":"affected","versionType":"git"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/bridge/br_multicast.c"],"versions":[{"version":"5.10","status":"affected"},{"version":"0","lessThan":"5.10","status":"unaffected","versionType":"semver"},{"version":"5.10.273","lessThanOrEqual":"5.10.*","status":"unaffected","versionType":"semver"},{"version":"5.15.224","lessThanOrEqual":"5.15.*","status":"unaffected","versionType":"semver"},{"version":"6.1.191","lessThanOrEqual":"6.1.*","status":"unaffected","versionType":"semver"},{"version":"6.6.161","lessThanOrEqual":"6.6.*","status":"unaffected","versionType":"semver"},{"version":"6.12.115","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.18.59","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"7.2.13","lessThanOrEqual":"7.2.*","status":"unaffected","versionType":"semver"},{"version":"7.3","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.10","versionEndExcluding":"5.10.273"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.10","versionEndExcluding":"5.15.224"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.10","versionEndExcluding":"6.1.191"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.10","versionEndExcluding":"6.6.161"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.10","versionEndExcluding":"6.12.115"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.10","versionEndExcluding":"6.18.59"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.10","versionEndExcluding":"7.2.13"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.10","versionEndExcluding":"7.3"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/be331b23c650de9518f8266b901d8abb9b36af77"},{"url":"https://git.kernel.org/stable/c/ab836d56ff43f2e7927e88c83cd02c47a98a672e"},{"url":"https://git.kernel.org/stable/c/025c25ad73323c7dc5af4ee97fe0a2c0b3c177c8"},{"url":"https://git.kernel.org/stable/c/b0db9f4ff402becff710ab27dbd9f6fe4850b47e"},{"url":"https://git.kernel.org/stable/c/e69d4927dacd6ddaff09777a89efc0d3143d3b0d"},{"url":"https://git.kernel.org/stable/c/8243d587a081e790ad96e80d48eef44d9f7ef005"},{"url":"https://git.kernel.org/stable/c/b45e8c24608c992d1e2cea047eb5bcbfa537f86b"},{"url":"https://git.kernel.org/stable/c/5a3f7a683aee56e1f15c9d53041f3236767eaae7"}],"title":"net: bridge: mcast: don't truncate the port group walk on teardown","x_generator":{"engine":"bippy-1.2.0"}}}}