CVE-2020-1919 : Exploit Details and Defense Strategies

Incorrect bounds calculations in substr_compare could lead to an out-of-bounds read when the second string argument passed in is longer than the first.

Understanding CVE-2020-1919

This CVE affects Facebook's HHVM versions and requires attention to prevent potential out-of-bounds reads.

What is CVE-2020-1919?

The vulnerability arises from incorrect bounds calculations in the substr_compare function, causing out-of-bounds read scenarios.

The Impact of CVE-2020-1919

The vulnerability can lead to out-of-bounds reads on affected systems, potentially resulting in unauthorized access or information disclosure.

Technical Details of CVE-2020-1919

Facebook's HHVM versions are susceptible to out-of-bounds reads due to incorrect bounds calculations.

Vulnerability Description

HHVM versions prior to 4.56.3 and between 4.57.0 to 4.80.1, 4.81.0 to 4.93.1, as well as versions 4.94.0 to 4.98.0 are affected.

Affected Systems and Versions

Product: HHVM
Vendor: Facebook
Affected Versions: 4.56.3 and below, 4.57.0 to 4.80.1, 4.81.0 to 4.93.1, 4.94.0 to 4.98.0

Exploitation Mechanism

Attackers can exploit this vulnerability by providing a second string argument longer than the first, triggering an out-of-bounds read.

Mitigation and Prevention

Actions to mitigate the risks associated with CVE-2020-1919

Immediate Steps to Take

Update HHVM to version 4.98.1 or implement appropriate patches provided by Facebook.
Monitor for any unauthorized access or unusual activities on the system.

Long-Term Security Practices

Regularly update and patch HHVM to the latest secure versions.
Conduct thorough security assessments and code reviews to prevent similar vulnerabilities.

Patching and Updates

Apply any security patches or updates released by Facebook promptly to address the vulnerability.