CVE-2019-3570
📋 TL;DR
CVE-2019-3570 is a heap corruption vulnerability in HHVM's scrypt_enc() function that allows attackers to overwrite memory by providing specially crafted scrypt parameters. This can lead to information disclosure, crashes, or remote code execution. Affected systems include HHVM versions 3.30.5 and below, all 4.0-4.2 series, and versions 4.3.0 through 4.8.0.
💻 Affected Systems
- HHVM (HipHop Virtual Machine)
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise, data exfiltration, or persistent backdoor installation.
Likely Case
HHVM process crashes causing service disruption, potential information disclosure through memory leaks.
If Mitigated
Denial of service through crashes if memory corruption doesn't lead to code execution.
🎯 Exploit Status
Exploitation requires understanding of scrypt parameters and heap corruption techniques, but no authentication is needed if scrypt_enc() is exposed.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 4.9.0 and later, 3.30.6 and later
Vendor Advisory: https://hhvm.com/blog/2019/06/10/hhvm-4.9.0.html
Restart Required: Yes
Instructions:
1. Upgrade HHVM to version 4.9.0 or later (or 3.30.6+ for 3.x series). 2. Restart HHVM service. 3. Verify the fix by checking version.
🔧 Temporary Workarounds
Disable scrypt_enc() usage
allModify application code to avoid using scrypt_enc() with untrusted parameters
Input validation for scrypt parameters
allImplement strict validation for N, r, p parameters before passing to scrypt_enc()
🧯 If You Can't Patch
- Implement network segmentation to isolate HHVM instances from untrusted networks
- Deploy web application firewall (WAF) rules to detect and block suspicious scrypt parameter patterns
🔍 How to Verify
Check if Vulnerable:
Check HHVM version: hhvm --version. If version matches affected range and scrypt_enc() is used, system is vulnerable.Check Version:
hhvm --versionVerify Fix Applied:
Verify HHVM version is 4.9.0+ or 3.30.6+ and test scrypt_enc() functionality with valid parameters.📡 Detection & Monitoring
Log Indicators:
- HHVM segmentation faults
- Memory corruption errors in HHVM logs
- Unexpected process termination
Network Indicators:
- Unusual requests to endpoints using scrypt functionality
- Repeated crashes of HHVM service
SIEM Query:
source="hhvm.log" AND ("segmentation fault" OR "memory corruption" OR "scrypt_enc")