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CVE-2026-31685

CRITICALCVSS 9.4/10EPSS 0.34%

Last modified

CVE-2026-31685 is a critical-severity vulnerability rated 9.4/10 on the CVSS scale. 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)`.. EPSS estimates a 0.34% chance of exploitation in the next 30 days.

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)`.

Metrics

CVSS 3.1
9.4/10

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

EPSS Probability
0.34%

25.6th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

VendorProductVersionsUpdate
LinuxLinux Kernel>= 2.6.12.1, < 6.6.136—
LinuxLinux Kernel>= 6.7, < 6.12.83—
LinuxLinux Kernel>= 6.13, < 6.18.24—
LinuxLinux Kernel>= 6.19, < 6.19.14—
LinuxLinux Kernel2.6.12—
LinuxLinux Kernel7.0Rc1

References

Timeline

Published
Last Modified
Status
Modified

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)`.
How severe is CVE-2026-31685?
CVE-2026-31685 has a CVSS score of 9.4/10 (CRITICAL severity). The EPSS model estimates a 0.34% probability of exploitation in the next 30 days.
How do I fix CVE-2026-31685?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2026-31685?

Run a free Strix scan to check your systems for this vulnerability.

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Source: NVD / NIST