CVE-2021-43836 Explained : Impact and Mitigation

Sulu is an open-source PHP content management system based on the Symfony framework. In affected versions, an attacker can read arbitrary local files via a PHP file include.

Understanding CVE-2021-43836

What is CVE-2021-43836?

In the Sulu content management system, versions prior to 1.6.44, between 2.0.0 and 2.2.18, and between 2.3.0 and 2.3.8 are vulnerable to PHP file inclusion, allowing an attacker to access local files.

The Impact of CVE-2021-43836

CVSS Base Score: 8.5 (High)
Attack Vector: Network
Impact: High impact on confidentiality, integrity, and availability
Vulnerability: Improper limitation of a pathname to a restricted directory

Technical Details of CVE-2021-43836

Vulnerability Description

The vulnerability allows unauthorized file access, potentially leading to remote code execution.

Affected Systems and Versions

Sulu versions < 1.6.44
Sulu versions >= 2.0.0 and < 2.2.18
Sulu versions >= 2.3.0 and < 2.3.8

Exploitation Mechanism

Attackers could exploit this vulnerability by using a PHP file include to read arbitrary local files, which can result in remote code execution.

Mitigation and Prevention

Immediate Steps to Take

Upgrade to patched versions 1.6.44, 2.2.18, 2.3.8, or 2.4.0
If unable to upgrade, overwrite the service

sulu_route.generator.expression_token_provider

to enhance security

Long-Term Security Practices

Regularly monitor and update the Sulu content management system
Implement secure coding practices to prevent similar vulnerabilities

Patching and Updates

Apply the available patches provided by Sulu to address the PHP file inclusion vulnerability.