High [CVE-2026-64032] Fix a possible use-after-free when removing a bridge port
This high-severity Red Hat Linux advisory covers CVE-2026-64032 affecting Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9, Shadow Migration Toolkit for Virtualization for RHEL 10.
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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 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.
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].
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative. Check it before change work.
Official advisory · high-confidence parse· fetched 7 days ago·verify at source
- kernel-0:6.12.0-211.66.1.el10_2
- kernel-0:5.14.0-687.59.1.el9_8
- RHSA-2026:83207
- RHSA-2026:86033
Official advisory · high-confidence parse· fetched 7 days ago·verify at source
Mitigation
Upgrade to a fixed release: kernel-0:6.12.0-211.66.1.el10_2, kernel-0:5.14.0-687.59.1.el9_8, RHSA-2026:83207, RHSA-2026:86033. That is the remediation for this advisory.
The vendor advisory may list interim mitigations or workarounds not captured here. Review it before change work.
Official advisory · high-confidence parse· fetched 7 days ago·verify at source
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