CVE-2020-1899 : Exploit Details and Defense Strategies

In June 2020, a vulnerability was identified in HHVM, a virtual machine designed for executing programs written in Hack and PHP. The vulnerability, assigned CVE-2020-1899, pertained to the unserialize() function and enabled unauthorized access to memory addresses within specific versions of HHVM.

Understanding CVE-2020-1899

What is CVE-2020-1899?

The vulnerability in HHVM's unserialize() function allowed for the unauthorized access of arbitrary memory addresses, posing a security risk in affected versions of the software.

The Impact of CVE-2020-1899

The vulnerability could potentially be exploited by attackers to gain unauthorized access to sensitive information or execute arbitrary code on systems running affected versions of HHVM.

Technical Details of CVE-2020-1899

Vulnerability Description

The unserialize() function in HHVM supported a type code, "S", intended only for APC serialization, enabling access to arbitrary memory addresses as static StringData objects.

Affected Systems and Versions

HHVM versions prior to v4.32.3
Versions between 4.33.0 and 4.56.0
Version 4.57.0
Version 4.58.0 and 4.58.1
Version 4.59.0
Version 4.60.0
Version 4.61.0
Version 4.62.0

Exploitation Mechanism

The vulnerability allowed attackers to access memory addresses as static StringData objects within the specified vulnerable versions of HHVM.

Mitigation and Prevention

Immediate Steps to Take

Upgrade HHVM to the latest unaffected version (4.62.1 or later)
Apply patches or security updates provided by the vendor
Monitor for any unauthorized access attempts

Long-Term Security Practices

Regularly update software to address security vulnerabilities
Implement secure coding practices to avoid similar issues in the future
Conduct security audits and penetration testing to identify weaknesses

Patching and Updates

Stay informed about security advisories and updates from the HHVM vendor
Apply patches promptly to ensure systems are protected against known vulnerabilities