{ "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" } } } }