CVE-2026-31685

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)`.

CVSS v3.1 Score

9.4

CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:H

EPSS — Exploit Prediction

0.0006

Probability of exploitation

0.19%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Affected Products

Vendor	Product	Versions
linux	linux_kernel	2.6.12.1 — 6.6.136
linux	linux_kernel	6.7 — 6.12.83
linux	linux_kernel	6.13 — 6.18.24
linux	linux_kernel	6.19 — 6.19.14
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All

References

Advisories & Patches

https://git.kernel.org/stable/c/288138418bef956f8b295751a4536c60f0e89f4a https://git.kernel.org/stable/c/309ae3e9a51a69699ca94eac5fac5688fa562d55 https://git.kernel.org/stable/c/807d6ee15804df6f01a35c910f09612e858739a6 https://git.kernel.org/stable/c/9eda5478746ef7dc0e4e537b5a5e4b0ca1027091 https://git.kernel.org/stable/c/fdce0b3590f724540795b874b4c8850c90e6b0a8

Frequently Asked Questions

What is CVE-2026-31685? +

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)`. It has a CVSS v3.1 base score of 9.4 (CRITICAL).

How severe is CVE-2026-31685? +

CVE-2026-31685 has a CVSS v3.1 score of 9.4 out of 10, rated CRITICAL. This is a critical vulnerability that should be patched immediately. The EPSS score is 0.0006, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-31685? +

CVE-2026-31685 affects products from linux, specifically: linux_kernel. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-31685? +

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.

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