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CVE-2026-31685

9.4 · CRITICAL

In the Linux kernel, the following vulnerability has been resolved: netfilter: ip6t_eui64: reject invalid MAC header for all packets `eui64_mt6()` derives a modified EUI-64 from the Ethernet sour…

Published Apr 25, 2026EPSS 0.39%

Overview

CVE-2026-31685 is a critical-severity vulnerability. It was published on April 25, 2026 and has a CVSS 3.1 base score of 9.4 (CRITICAL).

This vulnerability has a CVSS 3.1 base score of 9.4, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical description

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

netfilter: ip6t_eui64: reject invalid MAC header for all packets

`eui64_mt6()` derives a modified EUI-64 from the Ethernet source address

and compares it with the low 64 bits of the IPv6 source address.

The existing guard only rejects an invalid MAC header when

`par->fragoff != 0`. For packets with `par->fragoff == 0`, `eui64_mt6()`

can still reach `eth_hdr(skb)` even when the MAC header is not valid.

Fix this by removing the `par->fragoff != 0` condition so that packets

with an invalid MAC header are rejected before accessing `eth_hdr(skb)`.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

Refgit.kernel.org/stable/c/288138418bef956f8b295751a4536c60f0e89f4aRefgit.kernel.org/stable/c/309ae3e9a51a69699ca94eac5fac5688fa562d55Refgit.kernel.org/stable/c/4d75bc2cd093bf5803edf512c099bfb220fd6459Refgit.kernel.org/stable/c/7d6a57411caf54df025860c9b1a82cd42d57a562Refgit.kernel.org/stable/c/807d6ee15804df6f01a35c910f09612e858739a6Refgit.kernel.org/stable/c/9eda5478746ef7dc0e4e537b5a5e4b0ca1027091Refgit.kernel.org/stable/c/d5603591373441fecf9951833d6d873e09320f08Refgit.kernel.org/stable/c/fdce0b3590f724540795b874b4c8850c90e6b0a8

How CyberStrike helps

Frequently asked questions

What is CVE-2026-31685?

CVE-2026-31685 is a critical-severity vulnerability. It was published on April 25, 2026 and has a CVSS 3.1 base score of 9.4 (CRITICAL).

How severe is CVE-2026-31685?

This vulnerability has a CVSS 3.1 base score of 9.4, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-31685?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-31685?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-31685 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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