CVE-2019-11930
📋 TL;DR
CVE-2019-11930 is a critical memory corruption vulnerability in HHVM's mb_detect_order function that allows an invalid free operation. This can lead to application crashes or remote code execution. It affects multiple HHVM versions across different release branches.
💻 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 with full system compromise, allowing attackers to execute arbitrary code on the server.
Likely Case
Application crash leading to denial of service, with potential for memory corruption that could be leveraged for RCE.
If Mitigated
Application crash only, with proper memory protections preventing code execution.
🎯 Exploit Status
Exploitation requires triggering the vulnerable mb_detect_order function with specific inputs. Public proof-of-concept code exists demonstrating crash/DoS.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 3.30.12, 4.8.6, 4.23.2, 4.28.2 and later
Vendor Advisory: https://hhvm.com/blog/2019/10/28/security-update.html
Restart Required: Yes
Instructions:
1. Identify current HHVM version. 2. Upgrade to patched version: 3.30.12+, 4.8.6+, 4.23.2+, or 4.28.2+. 3. Restart HHVM service. 4. Verify the update was successful.
🔧 Temporary Workarounds
Disable mbstring extension
allTemporarily disable the vulnerable mbstring extension if not required
Edit HHVM configuration to remove or comment out mbstring extension
🧯 If You Can't Patch
- Implement strict input validation for all mbstring function calls
- Deploy web application firewall with memory corruption protection rules
🔍 How to Verify
Check if Vulnerable:
Check HHVM version against affected version ranges. If using vulnerable version and mbstring is enabled, system is vulnerable.Check Version:
hhvm --versionVerify Fix Applied:
Verify HHVM version is 3.30.12+, 4.8.6+, 4.23.2+, or 4.28.2+ and restart service.📡 Detection & Monitoring
Log Indicators:
- Segmentation fault errors in HHVM logs
- Unexpected process termination
- Memory corruption warnings
Network Indicators:
- Unusual requests to mbstring-related endpoints
- Repeated crash/restart patterns
SIEM Query:
source="hhvm.log" AND ("segmentation fault" OR "invalid free" OR "SIGSEGV")🔗 References
- https://github.com/facebook/hhvm/commit/524d2e60cfe910406ec6109e4286d7edd545ab36
- https://hhvm.com/blog/2019/10/28/security-update.html
- https://www.facebook.com/security/advisories/cve-2019-11930
- https://github.com/facebook/hhvm/commit/524d2e60cfe910406ec6109e4286d7edd545ab36
- https://hhvm.com/blog/2019/10/28/security-update.html
- https://www.facebook.com/security/advisories/cve-2019-11930
