CVE-2021-41186 Explained : Impact and Mitigation

Fluentd parser_apache2 plugin versions 0.14.14 to 1.14.1 are vulnerable to a Regular Expression Denial of Service (ReDoS) attack due to a specific pattern in Apache log files.

Understanding CVE-2021-41186

Fluentd's parser_apache2 plugin is susceptible to a ReDoS vulnerability leading to potential Denial of Service (DoS) attacks.

What is CVE-2021-41186?

Fluentd, a data collection and logging tool, is at risk of ReDoS due to inefficient regular expression processing in the parser_apache2 plugin.

The Impact of CVE-2021-41186

The vulnerability can be exploited remotely with high attack complexity, leading to significant availability impact.

Technical Details of CVE-2021-41186

The ReDoS vulnerability in the parser_apache2 plugin can disrupt services through long regular expression processing.

Vulnerability Description

A maliciously crafted Apache log can trigger excessive regular expression processing, potentially causing a DoS condition.

Affected Systems and Versions

Product:

fluentd

Vendor:

fluent

Versions Affected:

>= 0.14.14, < 1.14.2

Exploitation Mechanism

Attackers can send specially crafted Apache logs to trigger inefficient regular expression handling, potentially leading to service disruption.

Mitigation and Prevention

Immediate Steps to Take

Update to version 1.14.2 of Fluentd to patch the vulnerability.
Avoid using the parser_apache2 plugin for parsing Apache logs if upgrading is not feasible.

Long-Term Security Practices

Regularly monitor for security advisories and update software promptly.
Employ robust logging practices and implement intrusion detection systems.
Conduct regular security audits and vulnerability assessments.

Patching and Updates

Ensure timely application of security patches and follow best practices in software maintenance.