CVE-2020-1899
📋 TL;DR
CVE-2020-1899 is a memory corruption vulnerability in HHVM's unserialize() function that allows accessing arbitrary memory addresses via the 'S' type code. This can lead to remote code execution or information disclosure. Affects HHVM installations running vulnerable versions.
💻 Affected Systems
- HHVM (HipHop Virtual Machine)
📦 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
Application crash (denial of service) or memory disclosure leading to information leakage.
If Mitigated
Limited impact if proper network segmentation and least privilege are enforced, though still potentially serious.
🎯 Exploit Status
Requires unserialize() to be called with attacker-controlled data, which is common in web applications.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Fixed in 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. Upgrade to patched version based on your release branch. 3. Restart HHVM service. 4. Verify fix with version check.
🔧 Temporary Workarounds
Input validation for unserialize()
allValidate and sanitize all input passed to unserialize() functions.
Disable unserialize() on untrusted data
allAvoid using unserialize() with user-supplied data where possible.
🧯 If You Can't Patch
- Implement strict input validation for all data passed to unserialize() functions.
- Network segmentation to isolate HHVM instances from critical systems.
🔍 How to Verify
Check if Vulnerable:
Check HHVM version against affected version list. Review application code for unserialize() usage with untrusted input.Check Version:
hhvm --versionVerify Fix Applied:
Confirm HHVM version is patched (not in affected range) and restart service.📡 Detection & Monitoring
Log Indicators:
- HHVM crashes or abnormal termination logs
- Unusual memory access patterns in system logs
Network Indicators:
- Unexpected outbound connections from HHVM process
- Anomalous HTTP requests containing serialized data
SIEM Query:
source="hhvm.log" AND ("segmentation fault" OR "memory corruption" OR "unserialize")