bridge: mcast: Fix a possible use-after-free when removing a bridge port

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-64032
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-19 16:17:43 UTC
Updated2026-07-20 15:17:04 UTC
DescriptionIn 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>

Risk And Classification

Primary CVSS: v3.1 7.8 HIGH from 416baaa9-dc9f-4396-8d5f-8c081fb06d67

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS: 0.001720000 probability, percentile 0.069040000 (date 2026-07-20)

VersionSourceTypeScoreSeverityVector
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary7.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
3.1CNADECLARED7.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 410a033bfa8c7daefbae0225c836693db2149ec1 ddefd1b8e5eb58933a697ab38334f0fd82e7fb8b git Not specified
CNA Linux Linux affected c6d16eab122744df698f18b47cf771945cd55066 ed3b69e60385a03df11c6d12e5d7bdf0f4a11b70 git Not specified
CNA Linux Linux affected b4c83b37490d61cfdd62a2b29e98a9b89004b5c0 1900ca8acb92fbea8bf9abef9927c7fed03db7fc git Not specified
CNA Linux Linux affected 78f768e36c065ca3f88272fcf39014782c2d4ecd ebe5561154c823b323bd06e350b55e0b8604d851 git Not specified
CNA Linux Linux affected 4b30ae9adb047dd0a7982975ec3933c529537026 a9224862d597d0eed0a34bbb27343f703fc4113f git Not specified
CNA Linux Linux affected 4b30ae9adb047dd0a7982975ec3933c529537026 7213256c91ed778a0997c2029c152b18dc50e4fd git Not specified
CNA Linux Linux affected 4b30ae9adb047dd0a7982975ec3933c529537026 4df78ff02629c7729168f0696a7a2123c389818d git Not specified
CNA Linux Linux affected c996e25df0b3282c724bb5aca434518bc08cd963 git Not specified
CNA Linux Linux affected 5.15.186 5.15.209 semver Not specified
CNA Linux Linux affected 6.1.142 6.1.175 semver Not specified
CNA Linux Linux affected 6.6.95 6.6.142 semver Not specified
CNA Linux Linux affected 6.12.35 6.12.92 semver Not specified
CNA Linux Linux affected 6.15.4 6.16 semver Not specified
CNA Linux Linux affected 6.16 Not specified
CNA Linux Linux unaffected 6.16 semver Not specified
CNA Linux Linux unaffected 5.15.209 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.175 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.142 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.92 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.34 6.18.* semver Not specified
CNA Linux Linux unaffected 7.0.11 7.0.* semver Not specified
CNA Linux Linux unaffected 7.1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/ddefd1b8e5eb58933a697ab38334f0fd82e7fb8b 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/a9224862d597d0eed0a34bbb27343f703fc4113f 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/ebe5561154c823b323bd06e350b55e0b8604d851 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/4df78ff02629c7729168f0696a7a2123c389818d 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/ed3b69e60385a03df11c6d12e5d7bdf0f4a11b70 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/7213256c91ed778a0997c2029c152b18dc50e4fd 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/1900ca8acb92fbea8bf9abef9927c7fed03db7fc 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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