CVE-2020-1918 : Security Advisory and Response
Discover the HHVM memory access flaw in CVE-2020-1918. Learn the impacted versions, exploitation risks, and mitigation strategies to secure your systems.
A vulnerability in HHVM versions potentially allows reading memory prior to in-memory buffer due to improper restrictions during in-memory file operations.
Understanding CVE-2020-1918
What is CVE-2020-1918?
In-memory file operations (such as using fopen on a data URI) lack proper negative seeking restrictions, enabling memory access before the intended in-memory buffer.
The Impact of CVE-2020-1918
The vulnerability affects HHVM versions before 4.56.3, versions between 4.57.0 and 4.80.1, versions between 4.81.0 and 4.93.1, and versions 4.94.0, 4.95.0, 4.96.0, 4.97.0, and 4.98.0.
Technical Details of CVE-2020-1918
Vulnerability Description
The flaw allows unauthorized memory access during in-memory file operations, potentially leading to data leakage or unauthorized information retrieval.
Affected Systems and Versions
- HHVM versions prior to 4.56.3
- HHVM versions between 4.57.0 and 4.80.1
- HHVM versions between 4.81.0 and 4.93.1
- HHVM versions 4.94.0, 4.95.0, 4.96.0, 4.97.0, 4.98.0
Exploitation Mechanism
The issue occurs due to inadequate restrictions on seeking operations in in-memory file handling, leading to exposure of memory contents.
Mitigation and Prevention
Immediate Steps to Take
- Apply the latest patches provided by Facebook for HHVM
- Restrict file operations that involve in-memory processing
Long-Term Security Practices
- Regularly update HHVM to the latest version
- Implement secure coding practices to avoid memory access vulnerabilities
Patching and Updates
Ensure all HHVM instances are updated to versions that contain fixes for CVE-2020-1918.