netfilter: ip6t_eui64: reject invalid MAC header for all packets
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)`.
02 / AFFECTED SOFTWARE
Affected packages
1798 explicit affected versions
03 / CONNECTIONS
Connected vulnerabilities
04 / EVIDENCE
Source records
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)`.
05 / REFERENCES
Further evidence
- https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
- https://git.kernel.org/stable/c/288138418bef956f8b295751a4536c60f0e89f4a
- https://git.kernel.org/stable/c/309ae3e9a51a69699ca94eac5fac5688fa562d55
- https://git.kernel.org/stable/c/4d75bc2cd093bf5803edf512c099bfb220fd6459
- https://git.kernel.org/stable/c/7d6a57411caf54df025860c9b1a82cd42d57a562
- https://git.kernel.org/stable/c/807d6ee15804df6f01a35c910f09612e858739a6
- https://git.kernel.org/stable/c/9eda5478746ef7dc0e4e537b5a5e4b0ca1027091
- https://git.kernel.org/stable/c/d5603591373441fecf9951833d6d873e09320f08
- https://git.kernel.org/stable/c/fdce0b3590f724540795b874b4c8850c90e6b0a8
- https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31685.json
- https://nvd.nist.gov/vuln/detail/CVE-2026-31685