What’s Vulnerable › Vulnerabilities

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

• Severity: high (CVSS 7.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-11-12 · updated 2026-10-19

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.

Affected products

• Linux kernel: 4.7 — fixed in 6.18

How to fix

Upgrade to a fixed version: Linux kernel 6.18. Check the vendor advisory for mitigations.

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

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