From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-cve-announce@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@kernel.org>
Subject: CVE-2026-74480: net: bridge: stop fast-leave after deleting a port group
Date: Sat, 15 Aug 2026 21:26:01 +0900 [thread overview]
Message-ID: <2026081536-CVE-2026-74480-e620@gregkh> (raw)
From: Greg Kroah-Hartman <gregkh@kernel.org>
Description
===========
In the Linux kernel, the following vulnerability has been resolved:
net: bridge: stop fast-leave after deleting a port group
br_multicast_leave_group() iterates mp->ports with pp = &p->next in
its fast-leave path. After br_multicast_del_pg() removes p,
continuing the loop advances pp through the deleted entry.
If multicast-to-unicast was enabled, the bridge can hold multiple port
groups for the same port and group with different source MAC
addresses. Once multicast-to-unicast is disabled,
br_port_group_equal() matches those entries by port only. A fast leave
can then delete one entry and continue from its stale next pointer,
leaving mp->ports pointing at a deleted port group.
Fast leave only needs to remove one matching port group. Break after
br_multicast_del_pg() so the loop stops before dereferencing the
removed entry.
The Linux kernel CVE team has assigned CVE-2026-74480 to this issue.
Affected and fixed versions
===========================
Issue introduced in 4.11 with commit 6db6f0eae6052b70885562e1733896647ec1d807 and fixed in 6.6.151 with commit 159ad90cb929c033308bb39a2c5f8fbf393b77aa
Issue introduced in 4.11 with commit 6db6f0eae6052b70885562e1733896647ec1d807 and fixed in 6.12.103 with commit 4695430e8132420bf8de94da3eb36a6cf35fde6b
Issue introduced in 4.11 with commit 6db6f0eae6052b70885562e1733896647ec1d807 and fixed in 6.18.44 with commit 0309ebbc570000ea0df11c06b69798e5860c5f6f
Issue introduced in 4.11 with commit 6db6f0eae6052b70885562e1733896647ec1d807 and fixed in 7.1.8 with commit 4c57056ca6aace2e9f94ae9298bf49ef6b0c95e4
Issue introduced in 4.11 with commit 6db6f0eae6052b70885562e1733896647ec1d807 and fixed in 7.2-rc6 with commit a39789f211b8a4125f0c70e05b30cf715f4f187d
Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.
Unaffected versions might change over time as fixes are backported to
older supported kernel versions. The official CVE entry at
https://cve.org/CVERecord/?id=CVE-2026-74480
will be updated if fixes are backported, please check that for the most
up to date information about this issue.
Affected files
==============
The file(s) affected by this issue are:
net/bridge/br_multicast.c
Mitigation
==========
The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes. Individual
changes are never tested alone, but rather are part of a larger kernel
release. Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all. If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
https://git.kernel.org/stable/c/159ad90cb929c033308bb39a2c5f8fbf393b77aa
https://git.kernel.org/stable/c/4695430e8132420bf8de94da3eb36a6cf35fde6b
https://git.kernel.org/stable/c/0309ebbc570000ea0df11c06b69798e5860c5f6f
https://git.kernel.org/stable/c/4c57056ca6aace2e9f94ae9298bf49ef6b0c95e4
https://git.kernel.org/stable/c/a39789f211b8a4125f0c70e05b30cf715f4f187d
reply other threads:[~2026-08-15 12:29 UTC|newest]
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