CVE-2026-74475: vxlan: use neigh_ha_snapshot() in route_shortcircuit()

CVE-2026-74475: vxlan: use neigh_ha_snapshot() in route_shortcircuit()

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@kernel.org>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

vxlan: use neigh_ha_snapshot() in route_shortcircuit()

The neighbour hardware address n->ha can be updated asynchronously by the
neighbour subsystem, protected by n->ha_lock seqlock. Reading n->ha without
holding the seqlock loop can lead to torn reads or reading a partially updated
MAC address.

Use neigh_ha_snapshot() in route_shortcircuit() to safely copy n->ha under
read_seqbegin()/read_seqretry() lock protection before using it.

Note that arp_reduce() and neigh_reduce() seem to have the same issue
left for future patches.

The Linux kernel CVE team has assigned CVE-2026-74475 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 3.8 with commit e4f67addf158f98f8197e08974966b18480dc751 and fixed in 6.6.151 with commit d08e8ac13f2e228cc7fc3c70b5ebe71557b624a0
	Issue introduced in 3.8 with commit e4f67addf158f98f8197e08974966b18480dc751 and fixed in 6.12.103 with commit ec341bb76d77b4c2948764375ee6bfeef4bb41c3
	Issue introduced in 3.8 with commit e4f67addf158f98f8197e08974966b18480dc751 and fixed in 6.18.44 with commit ff89415d34c3ab9f5312316423122e664ed3524f
	Issue introduced in 3.8 with commit e4f67addf158f98f8197e08974966b18480dc751 and fixed in 7.1.8 with commit 05f2987f73daa05333fd713d05546142f9f7c5f0
	Issue introduced in 3.8 with commit e4f67addf158f98f8197e08974966b18480dc751 and fixed in 7.2-rc6 with commit 8eca411347e1d38964f9ed2c8d3b6ab0e7e4473d

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-2026-74475
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:
	drivers/net/vxlan/vxlan_core.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/d08e8ac13f2e228cc7fc3c70b5ebe71557b624a0
	https://git.kernel.org/stable/c/ec341bb76d77b4c2948764375ee6bfeef4bb41c3
	https://git.kernel.org/stable/c/ff89415d34c3ab9f5312316423122e664ed3524f
	https://git.kernel.org/stable/c/05f2987f73daa05333fd713d05546142f9f7c5f0
	https://git.kernel.org/stable/c/8eca411347e1d38964f9ed2c8d3b6ab0e7e4473d