CVE-2026-64032 (GCVE-0-2026-64032)
Vulnerability from cvelistv5
Published
2026-07-19 15:39
Modified
2026-10-19 20:28
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: bridge: mcast: Fix a possible use-after-free when removing a bridge port When per-VLAN multicast snooping is enabled, the bridge iterates over all the bridge ports, disables the per-port multicast context on each port and enables the per-{port, VLAN} multicast contexts instead. The reverse happens when per-VLAN multicast snooping is disabled. When global multicast snooping is enabled, the bridge iterates over all the bridge ports and enables the per-port multicast context on each port. The reverse happens when multicast snooping is disabled. The above scheme can result in a situation where both types of contexts (per-port and per-{port, VLAN}) are enabled on a single bridge port: # ip link add name br1 up type bridge mcast_snooping 1 mcast_querier 1 vlan_filtering 1 # ip link add name dummy1 up master br1 type dummy # ip link set dev br1 type bridge mcast_vlan_snooping 1 # ip link set dev br1 type bridge mcast_snooping 0 # ip link set dev br1 type bridge mcast_snooping 1 This is not intended and it is a problem since the commit cited below. Prior to this commit, when removing a bridge port, br_multicast_disable_port() would disable the per-port multicast context and the per-{port, VLAN} multicast contexts would get disabled when flushing VLANs. After this commit, br_multicast_disable_port() only disables the per-port multicast context if per-VLAN multicast snooping is disabled. If both types of contexts were enabled on the port when it was removed, the per-port multicast context would remain enabled when freeing the bridge port, leading to a use-after-free [1]. Fix by preventing the bridge from enabling / disabling the per-port multicast contexts when toggling global multicast snooping if per-VLAN multicast snooping is enabled. [1] ODEBUG: free active (active state 0) object: ffff88810f8bda78 object type: timer_list hint: br_ip6_multicast_port_query_expired (net/bridge/br_multicast.c:1927) WARNING: lib/debugobjects.c:629 at debug_print_object+0x1b1/0x3e0, CPU#5: swapper/5/0 [...] Call Trace: <IRQ> __debug_check_no_obj_freed (lib/debugobjects.c:1116) kfree (mm/slub.c:2620 mm/slub.c:6250 mm/slub.c:6565) kobject_cleanup (lib/kobject.c:689) rcu_do_batch (kernel/rcu/tree.c:2617) rcu_core (kernel/rcu/tree.c:2869) handle_softirqs (kernel/softirq.c:622) __irq_exit_rcu (kernel/softirq.c:656 kernel/softirq.c:496 kernel/softirq.c:735) irq_exit_rcu (kernel/softirq.c:752) sysvec_apic_timer_interrupt (arch/x86/kernel/apic/apic.c:1061 (discriminator 47) arch/x86/kernel/apic/apic.c:1061 (discriminator 47)) </IRQ>
References
Impacted products
Vendor Product Version
Linux Linux Version: 410a033bfa8c7daefbae0225c836693db2149ec1
Version: c6d16eab122744df698f18b47cf771945cd55066
Version: b4c83b37490d61cfdd62a2b29e98a9b89004b5c0
Version: 78f768e36c065ca3f88272fcf39014782c2d4ecd
Version: 4b30ae9adb047dd0a7982975ec3933c529537026
Version: 4b30ae9adb047dd0a7982975ec3933c529537026
Version: 4b30ae9adb047dd0a7982975ec3933c529537026
Version: c996e25df0b3282c724bb5aca434518bc08cd963
Version: 5.15.186   ≤
Version: 6.1.142   ≤
Version: 6.6.95   ≤
Version: 6.12.35   ≤
Version: 6.15.4   ≤
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbridge: mcast: Fix a possible use-after-free when removing a bridge port\n\nWhen per-VLAN multicast snooping is enabled, the bridge iterates over\nall the bridge ports, disables the per-port multicast context on each\nport and enables the per-{port, VLAN} multicast contexts instead. The\nreverse happens when per-VLAN multicast snooping is disabled.\n\nWhen global multicast snooping is enabled, the bridge iterates over all\nthe bridge ports and enables the per-port multicast context on each\nport. The reverse happens when multicast snooping is disabled.\n\nThe above scheme can result in a situation where both types of contexts\n(per-port and per-{port, VLAN}) are enabled on a single bridge port:\n\n # ip link add name br1 up type bridge mcast_snooping 1 mcast_querier 1 vlan_filtering 1\n # ip link add name dummy1 up master br1 type dummy\n # ip link set dev br1 type bridge mcast_vlan_snooping 1\n # ip link set dev br1 type bridge mcast_snooping 0\n # ip link set dev br1 type bridge mcast_snooping 1\n\nThis is not intended and it is a problem since the commit cited below.\nPrior to this commit, when removing a bridge port,\nbr_multicast_disable_port() would disable the per-port multicast context\nand the per-{port, VLAN} multicast contexts would get disabled when\nflushing VLANs.\n\nAfter this commit, br_multicast_disable_port() only disables the\nper-port multicast context if per-VLAN multicast snooping is disabled.\nIf both types of contexts were enabled on the port when it was removed,\nthe per-port multicast context would remain enabled when freeing the\nbridge port, leading to a use-after-free [1].\n\nFix by preventing the bridge from enabling / disabling the per-port\nmulticast contexts when toggling global multicast snooping if per-VLAN\nmulticast snooping is enabled.\n\n[1]\nODEBUG: free active (active state 0) object: ffff88810f8bda78 object type: timer_list hint: br_ip6_multicast_port_query_expired (net/bridge/br_multicast.c:1927)\nWARNING: lib/debugobjects.c:629 at debug_print_object+0x1b1/0x3e0, CPU#5: swapper/5/0\n[...]\nCall Trace:\n\u003cIRQ\u003e\n__debug_check_no_obj_freed (lib/debugobjects.c:1116)\nkfree (mm/slub.c:2620 mm/slub.c:6250 mm/slub.c:6565)\nkobject_cleanup (lib/kobject.c:689)\nrcu_do_batch (kernel/rcu/tree.c:2617)\nrcu_core (kernel/rcu/tree.c:2869)\nhandle_softirqs (kernel/softirq.c:622)\n__irq_exit_rcu (kernel/softirq.c:656 kernel/softirq.c:496 kernel/softirq.c:735)\nirq_exit_rcu (kernel/softirq.c:752)\nsysvec_apic_timer_interrupt (arch/x86/kernel/apic/apic.c:1061 (discriminator 47) arch/x86/kernel/apic/apic.c:1061 (discriminator 47))\n\u003c/IRQ\u003e"
        }
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            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
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              "lang": "en",
              "value": "AV:L - The vulnerable code is reached only through local bridge administration (rtnetlink RTM_NEWLINK, bridge ioctl, or sysfs), not through processing of remote network packets. An attacker must issue `ip link`/`bridge` configuration commands to create the inconsistent multicast state and remove a bridge port.\nAC:L - The reproducer sequence is fully attacker-controlled and deterministic; syzkaller triggered it reliably. The attacker configures the toggle sequence, removes the port, and the orphaned IGMP/MLD query timers fire on schedule without depending on uncontrollable timing or memory layout.\nPR:L - All entry paths require CAP_NET_ADMIN in the target network namespace (rtnetlink at rtnl_newlink, br_ioctl add_del_if, sysfs bridge attributes). Unprivileged local users can obtain this capability by creating a user+network namespace (`unshare -Urn`), which is widely enabled on server and container hosts.\nUI:N - Exploitation requires no action from any other user or victim; the attacker performs the entire bridge setup, state toggling, and port removal themselves.\nS:U - Successful exploitation corrupts kernel memory within the same kernel security domain. This is a standard local kernel memory corruption issue, not a cross-boundary escape such as VM guest-to-host or IOMMU bypass.\nC:H - This is a heap use-after-free on a freed net_bridge_port structure; the timer callback dereferences pmctx-\u003eport-\u003ebr on freed memory. UAF on kernel slab objects enables arbitrary kernel memory reads via heap grooming and reclamation of the freed port object.\nI:H - The UAF occurs in a timer softirq handler that reads and writes through fields of the freed port multicast context, including sending queries via br_multicast_send_query. Kernel heap UAF is exploitable for arbitrary write and control-flow hijack primitives, not merely a crash.\nA:H - The freed port structure is kfree\u0027d while IGMP/MLD own-query timers remain active, producing a debugobjects \"free active timer\" warning and use-after-free in softirq. This reliably causes kernel oops/panic and can be triggered repeatedly to deny service on shared infrastructure such as cloud hosts or software switches."
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      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:38:26.376Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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      "references": [
        {
          "url": "https://git.kernel.org/stable/c/ddefd1b8e5eb58933a697ab38334f0fd82e7fb8b"
        },
        {
          "url": "https://git.kernel.org/stable/c/ed3b69e60385a03df11c6d12e5d7bdf0f4a11b70"
        },
        {
          "url": "https://git.kernel.org/stable/c/1900ca8acb92fbea8bf9abef9927c7fed03db7fc"
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          "url": "https://git.kernel.org/stable/c/ebe5561154c823b323bd06e350b55e0b8604d851"
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          "url": "https://git.kernel.org/stable/c/a9224862d597d0eed0a34bbb27343f703fc4113f"
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        },
        {
          "url": "https://git.kernel.org/stable/c/4df78ff02629c7729168f0696a7a2123c389818d"
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      "title": "bridge: mcast: Fix a possible use-after-free when removing a bridge port",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-64032",
    "datePublished": "2026-07-19T15:39:22.228Z",
    "dateReserved": "2026-07-19T07:54:57.028Z",
    "dateUpdated": "2026-10-19T20:28:09.740Z",
    "state": "PUBLISHED"
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An attacker must issue `ip link`/`bridge` configuration commands to create the inconsistent multicast state and remove a bridge port.\\nAC:L - The reproducer sequence is fully attacker-controlled and deterministic; syzkaller triggered it reliably. The attacker configures the toggle sequence, removes the port, and the orphaned IGMP/MLD query timers fire on schedule without depending on uncontrollable timing or memory layout.\\nPR:L - All entry paths require CAP_NET_ADMIN in the target network namespace (rtnetlink at rtnl_newlink, br_ioctl add_del_if, sysfs bridge attributes). Unprivileged local users can obtain this capability by creating a user+network namespace (`unshare -Urn`), which is widely enabled on server and container hosts.\\nUI:N - Exploitation requires no action from any other user or victim; the attacker performs the entire bridge setup, state toggling, and port removal themselves.\\nS:U - Successful exploitation corrupts kernel memory within the same kernel security domain. This is a standard local kernel memory corruption issue, not a cross-boundary escape such as VM guest-to-host or IOMMU bypass.\\nC:H - This is a heap use-after-free on a freed net_bridge_port structure; the timer callback dereferences pmctx-\u003eport-\u003ebr on freed memory. UAF on kernel slab objects enables arbitrary kernel memory reads via heap grooming and reclamation of the freed port object.\\nI:H - The UAF occurs in a timer softirq handler that reads and writes through fields of the freed port multicast context, including sending queries via br_multicast_send_query. Kernel heap UAF is exploitable for arbitrary write and control-flow hijack primitives, not merely a crash.\\nA:H - The freed port structure is kfree\u0027d while IGMP/MLD own-query timers remain active, producing a debugobjects \\\"free active timer\\\" warning and use-after-free in softirq. This reliably causes kernel oops/panic and can be triggered repeatedly to deny service on shared infrastructure such as cloud hosts or software switches.\"}]}], \"affected\": [{\"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\", \"vendor\": \"Linux\", \"product\": \"Linux\", \"versions\": [{\"status\": \"affected\", \"version\": \"410a033bfa8c7daefbae0225c836693db2149ec1\", \"lessThan\": \"ddefd1b8e5eb58933a697ab38334f0fd82e7fb8b\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"c6d16eab122744df698f18b47cf771945cd55066\", \"lessThan\": \"ed3b69e60385a03df11c6d12e5d7bdf0f4a11b70\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"b4c83b37490d61cfdd62a2b29e98a9b89004b5c0\", \"lessThan\": \"1900ca8acb92fbea8bf9abef9927c7fed03db7fc\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"78f768e36c065ca3f88272fcf39014782c2d4ecd\", \"lessThan\": \"ebe5561154c823b323bd06e350b55e0b8604d851\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"4b30ae9adb047dd0a7982975ec3933c529537026\", \"lessThan\": \"a9224862d597d0eed0a34bbb27343f703fc4113f\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"4b30ae9adb047dd0a7982975ec3933c529537026\", \"lessThan\": \"7213256c91ed778a0997c2029c152b18dc50e4fd\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"4b30ae9adb047dd0a7982975ec3933c529537026\", \"lessThan\": \"4df78ff02629c7729168f0696a7a2123c389818d\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"c996e25df0b3282c724bb5aca434518bc08cd963\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"5.15.186\", \"lessThan\": \"5.15.209\", \"versionType\": \"semver\"}, {\"status\": \"affected\", \"version\": \"6.1.142\", \"lessThan\": \"6.1.175\", \"versionType\": \"semver\"}, {\"status\": \"affected\", \"version\": \"6.6.95\", \"lessThan\": \"6.6.142\", \"versionType\": \"semver\"}, {\"status\": \"affected\", \"version\": \"6.12.35\", \"lessThan\": \"6.12.92\", \"versionType\": \"semver\"}, {\"status\": \"affected\", \"version\": \"6.15.4\", \"lessThan\": \"6.16\", \"versionType\": \"semver\"}], \"programFiles\": [\"net/bridge/br_multicast.c\"], \"defaultStatus\": \"unaffected\"}, {\"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\", \"vendor\": \"Linux\", \"product\": \"Linux\", \"versions\": [{\"status\": \"affected\", \"version\": \"6.16\"}, {\"status\": \"unaffected\", \"version\": \"0\", \"lessThan\": \"6.16\", \"versionType\": \"semver\"}, {\"status\": \"unaffected\", \"version\": \"5.15.209\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.15.*\"}, {\"status\": \"unaffected\", \"version\": \"6.1.175\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.1.*\"}, {\"status\": \"unaffected\", \"version\": \"6.6.142\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.6.*\"}, {\"status\": \"unaffected\", \"version\": \"6.12.92\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.12.*\"}, {\"status\": \"unaffected\", \"version\": \"6.18.34\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.18.*\"}, {\"status\": \"unaffected\", \"version\": \"7.0.11\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"7.0.*\"}, {\"status\": \"unaffected\", \"version\": \"7.1\", \"versionType\": \"original_commit_for_fix\", \"lessThanOrEqual\": \"*\"}], \"programFiles\": [\"net/bridge/br_multicast.c\"], \"defaultStatus\": \"affected\"}], \"references\": [{\"url\": \"https://git.kernel.org/stable/c/ddefd1b8e5eb58933a697ab38334f0fd82e7fb8b\"}, {\"url\": \"https://git.kernel.org/stable/c/ed3b69e60385a03df11c6d12e5d7bdf0f4a11b70\"}, {\"url\": \"https://git.kernel.org/stable/c/1900ca8acb92fbea8bf9abef9927c7fed03db7fc\"}, {\"url\": \"https://git.kernel.org/stable/c/ebe5561154c823b323bd06e350b55e0b8604d851\"}, {\"url\": \"https://git.kernel.org/stable/c/a9224862d597d0eed0a34bbb27343f703fc4113f\"}, {\"url\": \"https://git.kernel.org/stable/c/7213256c91ed778a0997c2029c152b18dc50e4fd\"}, {\"url\": \"https://git.kernel.org/stable/c/4df78ff02629c7729168f0696a7a2123c389818d\"}], \"x_generator\": {\"engine\": \"bippy-1.2.0\"}, \"descriptions\": [{\"lang\": \"en\", \"value\": \"In the Linux kernel, the following vulnerability has been resolved:\\n\\nbridge: mcast: Fix a possible use-after-free when removing a bridge port\\n\\nWhen per-VLAN multicast snooping is enabled, the bridge iterates over\\nall the bridge ports, disables the per-port multicast context on each\\nport and enables the per-{port, VLAN} multicast contexts instead. The\\nreverse happens when per-VLAN multicast snooping is disabled.\\n\\nWhen global multicast snooping is enabled, the bridge iterates over all\\nthe bridge ports and enables the per-port multicast context on each\\nport. The reverse happens when multicast snooping is disabled.\\n\\nThe above scheme can result in a situation where both types of contexts\\n(per-port and per-{port, VLAN}) are enabled on a single bridge port:\\n\\n # ip link add name br1 up type bridge mcast_snooping 1 mcast_querier 1 vlan_filtering 1\\n # ip link add name dummy1 up master br1 type dummy\\n # ip link set dev br1 type bridge mcast_vlan_snooping 1\\n # ip link set dev br1 type bridge mcast_snooping 0\\n # ip link set dev br1 type bridge mcast_snooping 1\\n\\nThis is not intended and it is a problem since the commit cited below.\\nPrior to this commit, when removing a bridge port,\\nbr_multicast_disable_port() would disable the per-port multicast context\\nand the per-{port, VLAN} multicast contexts would get disabled when\\nflushing VLANs.\\n\\nAfter this commit, br_multicast_disable_port() only disables the\\nper-port multicast context if per-VLAN multicast snooping is disabled.\\nIf both types of contexts were enabled on the port when it was removed,\\nthe per-port multicast context would remain enabled when freeing the\\nbridge port, leading to a use-after-free [1].\\n\\nFix by preventing the bridge from enabling / disabling the per-port\\nmulticast contexts when toggling global multicast snooping if per-VLAN\\nmulticast snooping is enabled.\\n\\n[1]\\nODEBUG: free active (active state 0) object: ffff88810f8bda78 object type: timer_list hint: br_ip6_multicast_port_query_expired (net/bridge/br_multicast.c:1927)\\nWARNING: lib/debugobjects.c:629 at debug_print_object+0x1b1/0x3e0, CPU#5: swapper/5/0\\n[...]\\nCall Trace:\\n\u003cIRQ\u003e\\n__debug_check_no_obj_freed (lib/debugobjects.c:1116)\\nkfree (mm/slub.c:2620 mm/slub.c:6250 mm/slub.c:6565)\\nkobject_cleanup (lib/kobject.c:689)\\nrcu_do_batch (kernel/rcu/tree.c:2617)\\nrcu_core (kernel/rcu/tree.c:2869)\\nhandle_softirqs (kernel/softirq.c:622)\\n__irq_exit_rcu (kernel/softirq.c:656 kernel/softirq.c:496 kernel/softirq.c:735)\\nirq_exit_rcu (kernel/softirq.c:752)\\nsysvec_apic_timer_interrupt (arch/x86/kernel/apic/apic.c:1061 (discriminator 47) arch/x86/kernel/apic/apic.c:1061 (discriminator 47))\\n\u003c/IRQ\u003e\"}], \"cpeApplicability\": [{\"nodes\": [{\"negate\": false, \"cpeMatch\": [{\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.15.209\", \"versionStartIncluding\": \"5.15.186\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.1.175\", \"versionStartIncluding\": \"6.1.142\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.6.142\", \"versionStartIncluding\": \"6.6.95\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.12.92\", \"versionStartIncluding\": \"6.12.35\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.18.34\", \"versionStartIncluding\": \"6.16\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"7.0.11\", \"versionStartIncluding\": \"6.16\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"7.1\", \"versionStartIncluding\": \"6.16\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionStartIncluding\": \"6.15.4\"}], \"operator\": \"OR\"}]}], \"providerMetadata\": {\"orgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"shortName\": \"Linux\", \"dateUpdated\": \"2026-08-05T12:38:26.376Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-64032\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-10-16T15:42:19.942Z\", \"dateReserved\": \"2026-07-19T07:54:57.028Z\", \"assignerOrgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"datePublished\": \"2026-07-19T15:39:22.228Z\", \"assignerShortName\": \"Linux\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}


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