CVE-2021-41773 : Security Advisory and Response

A flaw in Apache HTTP Server 2.4.49 allows for path traversal attacks leading to remote code execution. It affects versions 2.4.49 and 2.4.50.

Understanding CVE-2021-41773

This CVE involves a critical vulnerability in the path normalization of Apache HTTP Server, enabling attackers to execute remote code.

What is CVE-2021-41773?

The flaw in Apache HTTP Server 2.4.49 allows path traversal attacks.
Attackers can map URLs to files outside configured directories.
Remote code execution is possible, mainly when CGI scripts are enabled.
Exploitation of this issue has been observed in the wild.

The Impact of CVE-2021-41773

Affected versions are Apache 2.4.49 and 2.4.50.
An incomplete fix was discovered in Apache HTTP Server 2.4.50.

Technical Details of CVE-2021-41773

The technical aspects of the vulnerability are as follows:

Vulnerability Description

Path traversal vulnerability impacting Apache HTTP Server.
Allows attackers to access files outside of configured directories.
Potential for remote code execution, especially with enabled CGI scripts.

Affected Systems and Versions

Affects Apache HTTP Server version 2.4.49 and the incomplete fix in version 2.4.50.

Exploitation Mechanism

Attackers exploit path normalization changes to conduct path traversal attacks.
By bypassing directory restrictions, attackers can execute remote code.

Mitigation and Prevention

Protect systems from CVE-2021-41773 using the following strategies:

Immediate Steps to Take

Apply security patches promptly.
Implement access controls to restrict unauthorized file access.
Disable unnecessary CGI script execution.

Long-Term Security Practices

Regularly monitor and update Apache HTTP Server.
Conduct security audits and penetration testing.

Patching and Updates

Ensure all Apache HTTP Server installations are updated to fixed versions.