CVE-2019-12831 Explained : Impact and Mitigation

MyBB before version 1.8.21 is vulnerable to a critical exploit that allows attackers to create a PHP shell in the cache directory of a targeted forum. This vulnerability, known as theme import stylesheet name RCE, leverages a default behavior of MySQL to truncate strings exceeding the database column length.

Understanding CVE-2019-12831

This CVE highlights a security flaw in MyBB versions prior to 1.8.21 that enables attackers to execute remote code through a crafted XML import.

What is CVE-2019-12831?

The vulnerability in MyBB allows malicious actors to manipulate XML imports to create a PHP shell in the cache directory of a specific forum by exploiting MySQL's default string truncation behavior.

The Impact of CVE-2019-12831

This vulnerability poses a severe risk as it can lead to unauthorized remote code execution on affected systems, compromising the security and integrity of the targeted forums.

Technical Details of CVE-2019-12831

MyBB's vulnerability to remote code execution through theme import stylesheet manipulation.

Vulnerability Description

The flaw arises from the truncation of file extensions in XML imports, enabling attackers to create PHP shells in the cache directory.

Affected Systems and Versions

MyBB versions before 1.8.21

Exploitation Mechanism

Attackers exploit MySQL's default behavior to truncate strings, creating a PHP shell in the cache directory.

Mitigation and Prevention

Protecting systems from CVE-2019-12831 requires immediate action and long-term security measures.

Immediate Steps to Take

Update MyBB to version 1.8.21 or later to patch the vulnerability.
Monitor forum activities for suspicious behavior.

Long-Term Security Practices

Regularly update and patch software to prevent known vulnerabilities.
Implement strong access controls and user permissions to limit potential exploits.
Conduct security audits and penetration testing to identify and address weaknesses.
Educate users on safe practices to mitigate social engineering attacks.

Patching and Updates

Apply security patches promptly to ensure protection against known vulnerabilities.