CVE-2026-72051: net: ip6_tunnel: require CAP_NET_ADMIN in the device netns for changelink

From: Greg Kroah-Hartman <[email protected]>

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

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

net: ip6_tunnel: require CAP_NET_ADMIN in the device netns for changelink

ip6_tnl_changelink() operates on at most two netns, dev_net(dev) and the
tunnel link netns t->net. They differ once the device is created in or
moved to a netns other than the one the request runs in. The rtnl
changelink path checks CAP_NET_ADMIN only against dev_net(dev), so a
caller privileged there but not in t->net can rewrite a tunnel that
lives in t->net.

Gate ip6_tnl_changelink() on rtnl_dev_link_net_capable() at its top,
before any attribute is parsed.

The Linux kernel CVE team has assigned CVE-2026-72051 to this issue.


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

	Issue introduced in 3.12 with commit 0bd8762824e73a3cce7b7560a97463301764b616 and fixed in 6.6.148 with commit 2636d061bc237a2446a146e42dcc6563acfa7432
	Issue introduced in 3.12 with commit 0bd8762824e73a3cce7b7560a97463301764b616 and fixed in 6.12.101 with commit 7f68f7928484f463a5bc0d50e6fdd8d16f55a5aa
	Issue introduced in 3.12 with commit 0bd8762824e73a3cce7b7560a97463301764b616 and fixed in 6.18.40 with commit 234cd54fc500f69db43e37de38603da617fbbeea
	Issue introduced in 3.12 with commit 0bd8762824e73a3cce7b7560a97463301764b616 and fixed in 7.1.5 with commit d4bcc202a3530c856e1cb183384bc9cc8fddab22
	Issue introduced in 3.12 with commit 0bd8762824e73a3cce7b7560a97463301764b616 and fixed in 7.2-rc1 with commit 2496fa0b7d180b3ad356b514e7ff93bb14e6140a

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-2026-72051
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/ipv6/ip6_tunnel.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/2636d061bc237a2446a146e42dcc6563acfa7432
	https://git.kernel.org/stable/c/7f68f7928484f463a5bc0d50e6fdd8d16f55a5aa
	https://git.kernel.org/stable/c/234cd54fc500f69db43e37de38603da617fbbeea
	https://git.kernel.org/stable/c/d4bcc202a3530c856e1cb183384bc9cc8fddab22
	https://git.kernel.org/stable/c/2496fa0b7d180b3ad356b514e7ff93bb14e6140a