Linux Kernel Netfilter EUI-64 Address Validation Bypass
CVE-2026-31685 Published on April 25, 2026
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)`.
Products Associated with CVE-2026-31685
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Affected Versions
Linux:- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below 9eda5478746ef7dc0e4e537b5a5e4b0ca1027091 is affected.
- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below 807d6ee15804df6f01a35c910f09612e858739a6 is affected.
- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below 309ae3e9a51a69699ca94eac5fac5688fa562d55 is affected.
- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below fdce0b3590f724540795b874b4c8850c90e6b0a8 is affected.
- Version 2.6.12 is affected.
- Before 2.6.12 is unaffected.
- Version 6.12.83, <= 6.12.* is unaffected.
- Version 6.18.24, <= 6.18.* is unaffected.
- Version 6.19.14, <= 6.19.* is unaffected.
- Version 7.0, <= * is unaffected.