CVE-2026-64032 (GCVE-0-2026-64032)
Vulnerability from cvelistv5
Published
2026-07-19 15:39
Modified
2026-08-05 12:38
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   ≤
Create a notification for this product.
Show details on NVD website

To clipboard 

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/bridge/br_multicast.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "ddefd1b8e5eb58933a697ab38334f0fd82e7fb8b",
              "status": "affected",
              "version": "410a033bfa8c7daefbae0225c836693db2149ec1",
              "versionType": "git"
            },
            {
              "lessThan": "ed3b69e60385a03df11c6d12e5d7bdf0f4a11b70",
              "status": "affected",
              "version": "c6d16eab122744df698f18b47cf771945cd55066",
              "versionType": "git"
            },
            {
              "lessThan": "1900ca8acb92fbea8bf9abef9927c7fed03db7fc",
              "status": "affected",
              "version": "b4c83b37490d61cfdd62a2b29e98a9b89004b5c0",
              "versionType": "git"
            },
            {
              "lessThan": "ebe5561154c823b323bd06e350b55e0b8604d851",
              "status": "affected",
              "version": "78f768e36c065ca3f88272fcf39014782c2d4ecd",
              "versionType": "git"
            },
            {
              "lessThan": "a9224862d597d0eed0a34bbb27343f703fc4113f",
              "status": "affected",
              "version": "4b30ae9adb047dd0a7982975ec3933c529537026",
              "versionType": "git"
            },
            {
              "lessThan": "7213256c91ed778a0997c2029c152b18dc50e4fd",
              "status": "affected",
              "version": "4b30ae9adb047dd0a7982975ec3933c529537026",
              "versionType": "git"
            },
            {
              "lessThan": "4df78ff02629c7729168f0696a7a2123c389818d",
              "status": "affected",
              "version": "4b30ae9adb047dd0a7982975ec3933c529537026",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "c996e25df0b3282c724bb5aca434518bc08cd963",
              "versionType": "git"
            },
            {
              "lessThan": "5.15.209",
              "status": "affected",
              "version": "5.15.186",
              "versionType": "semver"
            },
            {
              "lessThan": "6.1.175",
              "status": "affected",
              "version": "6.1.142",
              "versionType": "semver"
            },
            {
              "lessThan": "6.6.142",
              "status": "affected",
              "version": "6.6.95",
              "versionType": "semver"
            },
            {
              "lessThan": "6.12.92",
              "status": "affected",
              "version": "6.12.35",
              "versionType": "semver"
            },
            {
              "lessThan": "6.16",
              "status": "affected",
              "version": "6.15.4",
              "versionType": "semver"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/bridge/br_multicast.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.16"
            },
            {
              "lessThan": "6.16",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.209",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.175",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.142",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.92",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.34",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.0.*",
              "status": "unaffected",
              "version": "7.0.11",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.15.209",
                  "versionStartIncluding": "5.15.186",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.1.175",
                  "versionStartIncluding": "6.1.142",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.142",
                  "versionStartIncluding": "6.6.95",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.92",
                  "versionStartIncluding": "6.12.35",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.34",
                  "versionStartIncluding": "6.16",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.0.11",
                  "versionStartIncluding": "6.16",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.1",
                  "versionStartIncluding": "6.16",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionStartIncluding": "6.15.4",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "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"
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "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"
          },
          "scenarios": [
            {
              "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."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:38:26.376Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "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"
        }
      ],
      "title": "bridge: mcast: Fix a possible use-after-free when removing a bridge port",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-64032",
    "datePublished": "2026-07-19T15:39:22.228Z",
    "dateReserved": "2026-07-19T07:54:57.028Z",
    "dateUpdated": "2026-08-05T12:38:26.376Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


Log in or create an account to share your comment.




Tags
Taxonomy of the tags.




Sightings

Author Source Type Date

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
  • Confirmed: The vulnerability is confirmed from an analyst perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
  • Patched: This vulnerability was successfully patched by the user reporting the sighting.
  • Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
  • Not confirmed: The user expresses doubt about the veracity of the vulnerability.
  • Not patched: This vulnerability was not successfully patched by the user reporting the sighting.