CVE-2025-40173
Published Nov 12, 2025
Modified Apr 15, 2026
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.
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References
Other References
https://git.kernel.org/stable/c/10fe967efe73c610e526ff7460581610633dee9c
https://git.kernel.org/stable/c/11f6066af3bfb8149aa16c42c0b0c5ea5b199a94
https://git.kernel.org/stable/c/21f4d45eba0b2dcae5dbc9e5e0ad08735c993f16
https://git.kernel.org/stable/c/402b6985e872b4cf394bbbf33b503947a326a6cb
https://git.kernel.org/stable/c/48294a67863c9cfa367abb66bbf0ef6548ae124f
https://git.kernel.org/stable/c/566f8d5c8a443f2dd69c5460fdec43ed1c870c65
https://git.kernel.org/stable/c/b6eb25d870f1a8ae571fd3da2244b71df547824b
https://git.kernel.org/stable/c/eeb4345488672584db4f8c20a1ae13a212ce31c4
Frequently Asked Questions
What is CVE-2025-40173? +
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.
How do I check if I'm vulnerable to CVE-2025-40173? +
You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.