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Fencer Vulns
high 7.8

CVE-2026-64032 json

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

published 2026-07-19 3 mo ago modified 2026-10-19 20 d ago also EUVD-2026-45605

cvss
7.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.1%
EPSS 0.1% chance of exploitation in 30 days, percentile 2%
public exploits
0
none known

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>

Patch / fix

  • Linux Linux 5.15.209, 6.1.175, 6.6.142, 6.12.92, 6.16, 6.18.34, 7.0.11, 7.1
  • linux Debian 12 6.1.176-1
  • linux Debian 13 6.12.94-1
  • linux Debian 14 7.0.12-1

debian advisories DEBIAN-CVE-2026-64032

  • linux Ubuntu 22.04 LTS 5.15.0-186.196
  • linux Ubuntu 24.04 LTS 6.8.0-139.139
  • linux Ubuntu 26.04 LTS 7.0.0-28.28
  • linux-aws Ubuntu 22.04 LTS 5.15.0-1112.119
  • linux-aws Ubuntu 24.04 LTS 6.8.0-1064.67
  • linux-aws Ubuntu 26.04 LTS 7.0.0-1009.9
  • linux-gcp Ubuntu 22.04 LTS 5.15.0-1112.122
  • linux-gcp Ubuntu 24.04 LTS 6.8.0-1067.75

ubuntu advisories UBUNTU-CVE-2026-64032

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • kernel RHEL 10.2 6.12.0-211.66.1.el10_2
  • rv RHEL 10.2 6.12.0-211.66.1.el10_2
  • perf RHEL 10.2 6.12.0-211.66.1.el10_2
  • rtla RHEL 10.2 6.12.0-211.66.1.el10_2
  • libperf RHEL 10.2 6.12.0-211.66.1.el10_2
  • kernel-rt RHEL 10.2 6.12.0-211.66.1.el10_2
  • kernel-64k RHEL 10.2 6.12.0-211.66.1.el10_2
  • kernel-core RHEL 10.2 6.12.0-211.66.1.el10_2

red hat advisories RHSA-2026:83207

  • kernel AlmaLinux 9 5.14.0-687.59.1.el9_8
  • rv AlmaLinux 9 5.14.0-687.59.1.el9_8
  • perf AlmaLinux 9 5.14.0-687.59.1.el9_8
  • rtla AlmaLinux 9 5.14.0-687.59.1.el9_8
  • libperf AlmaLinux 9 5.14.0-687.59.1.el9_8
  • kernel-rt AlmaLinux 9 5.14.0-687.59.1.el9_8
  • kernel-64k AlmaLinux 9 5.14.0-687.59.1.el9_8
  • kernel-core AlmaLinux 9 5.14.0-687.59.1.el9_8

almalinux advisories ALSA-2026:86033ALSA-2026:83207

  • kernel Rocky Linux 9 5.14.0-687.59.1.el9_8
  • kernel Rocky Linux 10 6.12.0-211.66.1.el10_2

rocky linux advisories RLSA-2026:86033RLSA-2026:83207

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-64032 updated cvss 7.8

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

  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more
    affected: workaround, no fix planned “Out of support scope”
  • Red Hat Enterprise Linux kernel-modules-internal 6.12.0-211.66.1.el10_2
    fixed: vendor fix RHSA-2026:83207
  • Red Hat Enterprise Linux AppStream (v. 9) rv 5.14.0-687.59.1.el9_8, perf 5.14.0-687.59.1.el9_8, rtla 5.14.0-687.59.1.el9_8, python3-perf 5.14.0-687.59.1.el9_8, kernel-devel-matched 5.14.0-687.59.1.el9_8, kernel-64k-devel-matched 5.14.0-687.59.1.el9_8, +7 more
    fixed: vendor fix RHSA-2026:86033
  • Red Hat Enterprise Linux AppStream (v. 10) rv 6.12.0-211.66.1.el10_2, perf 6.12.0-211.66.1.el10_2, rtla 6.12.0-211.66.1.el10_2, python3-perf 6.12.0-211.66.1.el10_2, kernel-devel-matched 6.12.0-211.66.1.el10_2, kernel-64k-devel-matched 6.12.0-211.66.1.el10_2, +7 more
    fixed: vendor fix RHSA-2026:83207
  • Red Hat Enterprise Linux BaseOS (v. 9) kernel 5.14.0-687.59.1.el9_8, kernel-64k 5.14.0-687.59.1.el9_8, kernel-core 5.14.0-687.59.1.el9_8, kernel-tools 5.14.0-687.59.1.el9_8, kernel-modules 5.14.0-687.59.1.el9_8, kernel-64k-core 5.14.0-687.59.1.el9_8, +27 more
    fixed: vendor fix RHSA-2026:86033
  • Red Hat Enterprise Linux BaseOS (v. 10) kernel 6.12.0-211.66.1.el10_2, kernel-64k 6.12.0-211.66.1.el10_2, kernel-core 6.12.0-211.66.1.el10_2, kernel-tools 6.12.0-211.66.1.el10_2, kernel-modules 6.12.0-211.66.1.el10_2, kernel-64k-core 6.12.0-211.66.1.el10_2, +28 more
    fixed: vendor fix RHSA-2026:83207
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) libperf 5.14.0-687.59.1.el9_8, kernel-debuginfo-common-s390x 5.14.0-687.59.1.el9_8, kernel-debuginfo-common-x86_64 5.14.0-687.59.1.el9_8, kernel-debuginfo-common-aarch64 5.14.0-687.59.1.el9_8, kernel-debuginfo-common-ppc64le 5.14.0-687.59.1.el9_8
    fixed: vendor fix RHSA-2026:86033
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) libperf 6.12.0-211.66.1.el10_2, kernel-debuginfo-common-s390x 6.12.0-211.66.1.el10_2, kernel-debuginfo-common-x86_64 6.12.0-211.66.1.el10_2, kernel-debuginfo-common-aarch64 6.12.0-211.66.1.el10_2, kernel-debuginfo-common-ppc64le 6.12.0-211.66.1.el10_2 Red Hat Enterprise Linux Hidden (v. 10) kernel-modules-internal 6.12.0-211.66.1.el10_2, kernel-debuginfo-common-x86_64 6.12.0-211.66.1.el10_2
    fixed: vendor fix RHSA-2026:83207
show 5 more
  • Red Hat Enterprise Linux Real Time (v. 9) kernel-rt 5.14.0-687.59.1.el9_8, kernel-rt-64k 5.14.0-687.59.1.el9_8, kernel-rt-core 5.14.0-687.59.1.el9_8, kernel-rt-modules 5.14.0-687.59.1.el9_8, kernel-rt-64k-core 5.14.0-687.59.1.el9_8, kernel-rt-debug-core 5.14.0-687.59.1.el9_8, +14 more
    fixed: vendor fix RHSA-2026:86033
  • Red Hat Enterprise Linux Real Time (v. 10) kernel-rt 6.12.0-211.66.1.el10_2, kernel-rt-64k 6.12.0-211.66.1.el10_2, kernel-rt-core 6.12.0-211.66.1.el10_2, kernel-rt-modules 6.12.0-211.66.1.el10_2, kernel-rt-64k-core 6.12.0-211.66.1.el10_2, kernel-rt-debug-core 6.12.0-211.66.1.el10_2, +14 more
    fixed: vendor fix RHSA-2026:83207
  • Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt 5.14.0-687.59.1.el9_8, kernel-rt-core 5.14.0-687.59.1.el9_8, kernel-rt-modules 5.14.0-687.59.1.el9_8, kernel-rt-debug-core 5.14.0-687.59.1.el9_8, kernel-rt-modules-core 5.14.0-687.59.1.el9_8, kernel-rt-debug-modules 5.14.0-687.59.1.el9_8, +4 more
    fixed: vendor fix RHSA-2026:86033
  • Red Hat Enterprise Linux Real Time for NFV (v. 10) kernel-rt 6.12.0-211.66.1.el10_2, kernel-rt-core 6.12.0-211.66.1.el10_2, kernel-rt-modules 6.12.0-211.66.1.el10_2, kernel-rt-debug-core 6.12.0-211.66.1.el10_2, kernel-rt-modules-core 6.12.0-211.66.1.el10_2, kernel-rt-debug-modules 6.12.0-211.66.1.el10_2, +4 more
    fixed: vendor fix RHSA-2026:83207
  • Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 kernel-rt, kernel-rt-kvm, kernel-rt-core, kernel-rt-modules, kernel-rt-debug-kvm, kernel-rt-debug-core, +12 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
23 d ago

Exploit prediction

0.13% chance of exploitation in the next 30 days, higher than 2% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected products

  • Linux Linux

Classification

Weakness
Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.