linux-cve-announce - CVE-2025-40173: net/ip6_tunnel: Prevent perpetual tunnel growth

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Message-ID: <2025111254-CVE-2025-40173-4a68@gregkh>
Date: Wed, 12 Nov 2025 05:53:56 -0500
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-40173: net/ip6_tunnel: Prevent perpetual tunnel growth

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

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

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

net/ip6_tunnel: Prevent perpetual tunnel growth

Similarly to ipv4 tunnel, ipv6 version updates dev->needed_headroom, too.
While ipv4 tunnel headroom adjustment growth was limited in
commit 5ae1e9922bbd ("net: ip_tunnel: prevent perpetual headroom growth"),
ipv6 tunnel yet increases the headroom without any ceiling.

Reflect ipv4 tunnel headroom adjustment limit on ipv6 version.

Credits to Francesco Ruggeri, who was originally debugging this issue
and wrote local Arista-specific patch and a reproducer.

The Linux kernel CVE team has assigned CVE-2025-40173 to this issue.


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

	Issue introduced in 4.7 with commit 8eb30be0352d09165e94a41fef1c7b994dca0714 and fixed in 5.4.301 with commit 566f8d5c8a443f2dd69c5460fdec43ed1c870c65
	Issue introduced in 4.7 with commit 8eb30be0352d09165e94a41fef1c7b994dca0714 and fixed in 5.10.246 with commit 11f6066af3bfb8149aa16c42c0b0c5ea5b199a94
	Issue introduced in 4.7 with commit 8eb30be0352d09165e94a41fef1c7b994dca0714 and fixed in 5.15.196 with commit 402b6985e872b4cf394bbbf33b503947a326a6cb
	Issue introduced in 4.7 with commit 8eb30be0352d09165e94a41fef1c7b994dca0714 and fixed in 6.1.158 with commit 10fe967efe73c610e526ff7460581610633dee9c
	Issue introduced in 4.7 with commit 8eb30be0352d09165e94a41fef1c7b994dca0714 and fixed in 6.6.114 with commit 48294a67863c9cfa367abb66bbf0ef6548ae124f
	Issue introduced in 4.7 with commit 8eb30be0352d09165e94a41fef1c7b994dca0714 and fixed in 6.12.55 with commit eeb4345488672584db4f8c20a1ae13a212ce31c4
	Issue introduced in 4.7 with commit 8eb30be0352d09165e94a41fef1c7b994dca0714 and fixed in 6.17.5 with commit b6eb25d870f1a8ae571fd3da2244b71df547824b
	Issue introduced in 4.7 with commit 8eb30be0352d09165e94a41fef1c7b994dca0714 and fixed in 6.18-rc2 with commit 21f4d45eba0b2dcae5dbc9e5e0ad08735c993f16

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-2025-40173
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:
	include/net/ip_tunnels.h
	net/ipv4/ip_tunnel.c
	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/566f8d5c8a443f2dd69c5460fdec43ed1c870c65
	https://git.kernel.org/stable/c/11f6066af3bfb8149aa16c42c0b0c5ea5b199a94
	https://git.kernel.org/stable/c/402b6985e872b4cf394bbbf33b503947a326a6cb
	https://git.kernel.org/stable/c/10fe967efe73c610e526ff7460581610633dee9c
	https://git.kernel.org/stable/c/48294a67863c9cfa367abb66bbf0ef6548ae124f
	https://git.kernel.org/stable/c/eeb4345488672584db4f8c20a1ae13a212ce31c4
	https://git.kernel.org/stable/c/b6eb25d870f1a8ae571fd3da2244b71df547824b
	https://git.kernel.org/stable/c/21f4d45eba0b2dcae5dbc9e5e0ad08735c993f16