CVE-2019-9749 : Exploit Details and Defense Strategies

A vulnerability was found in the MQTT input plugin in Fluent Bit version 1.0.4, where the plugin fails to handle incoming network messages properly, leading to a server crash.

Understanding CVE-2019-9749

This CVE identifies a flaw in the MQTT input plugin in Fluent Bit version 1.0.4 that can be exploited to crash the server.

What is CVE-2019-9749?

The vulnerability in the MQTT input plugin in Fluent Bit version 1.0.4 allows attackers to crash the server by sending a specially crafted packet that triggers a SIGSEGV signal.

The Impact of CVE-2019-9749

The entire Fluent Bit server crashes due to a SIGSEGV signal when the plugin fails to handle incoming network messages properly.

Technical Details of CVE-2019-9749

This section provides detailed technical information about the vulnerability.

Vulnerability Description

The issue occurs in the MQTT input plugin in Fluent Bit version 1.0.4 when functioning as an MQTT broker and mishandling incoming network messages. The crash is triggered by executing the memmove() function with a negative size parameter.

Affected Systems and Versions

Product: Fluent Bit
Version: 1.0.4

Exploitation Mechanism

Attackers send a specially crafted packet to the MQTT input plugin in Fluent Bit version 1.0.4
The plugin's mqtt_packet_drop function executes the memmove() function with a negative size parameter
This leads to a crash of the entire Fluent Bit server via a SIGSEGV signal

Mitigation and Prevention

Protect your systems from CVE-2019-9749 by following these mitigation strategies.

Immediate Steps to Take

Update Fluent Bit to a patched version that addresses the vulnerability
Monitor network traffic for any suspicious activity

Long-Term Security Practices

Regularly update software and plugins to the latest versions
Implement network intrusion detection systems to detect and prevent similar attacks

Patching and Updates

Apply patches provided by Fluent Bit to fix the vulnerability