CVE-2020-1900
📋 TL;DR
CVE-2020-1900 is a use-after-free vulnerability in HHVM's object unserialization that occurs when dynamic properties are not properly pre-reserved in memory arrays. This allows attackers to potentially execute arbitrary code or cause denial of service. Affected systems are those running vulnerable versions of HHVM.
💻 Affected Systems
- HHVM
📦 What is this software?
Hhvm by Facebook
Hhvm by Facebook
Hhvm by Facebook
Hhvm by Facebook
Hhvm by Facebook
Hhvm by Facebook
Hhvm by Facebook
Hhvm by Facebook
Hhvm by Facebook
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise, data theft, or ransomware deployment.
Likely Case
Denial of service through application crashes or memory corruption, potentially leading to data loss.
If Mitigated
Limited impact if proper input validation and serialization controls are implemented.
🎯 Exploit Status
Exploitation requires crafting malicious serialized objects, but no public exploit code is available.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: v4.32.3, v4.56.1, v4.57.1, v4.58.2, v4.59.1, v4.60.1, v4.61.1, v4.62.1 and later
Vendor Advisory: https://hhvm.com/blog/2020/06/30/security-update.html
Restart Required: Yes
Instructions:
1. Identify current HHVM version. 2. Update to patched version using package manager. 3. Restart HHVM service. 4. Verify version after restart.
🔧 Temporary Workarounds
Disable unserialize of untrusted data
allImplement input validation to prevent unserialization of user-controlled data
Use safe serialization alternatives
allReplace unserialize() with JSON decode or other safe data formats
🧯 If You Can't Patch
- Implement strict input validation to reject serialized objects from untrusted sources
- Deploy web application firewall rules to detect and block serialized object payloads
🔍 How to Verify
Check if Vulnerable:
Check HHVM version with: hhvm --versionCheck Version:
hhvm --versionVerify Fix Applied:
Verify version is patched (v4.32.3+, v4.56.1+, etc.) and test unserialization functionality📡 Detection & Monitoring
Log Indicators:
- Memory corruption errors
- Segmentation faults in HHVM logs
- Unusual unserialization patterns
Network Indicators:
- Malformed serialized objects in HTTP requests
- Unexpected HHVM process crashes
SIEM Query:
source="hhvm.log" AND ("segmentation fault" OR "memory corruption" OR "unserialize")