CVE-2016-7955
📋 TL;DR
This authentication bypass vulnerability in AlienVault OSSIM and USM allows remote attackers to gain root access by sending a specially crafted HTTP User-Agent header. Attackers can execute arbitrary code, modify the application, or access sensitive information. Organizations running affected versions of AlienVault security monitoring products are vulnerable.
💻 Affected Systems
- AlienVault OSSIM
- AlienVault USM
📦 What is this software?
Ossim by Alienvault
⚠️ Risk & Real-World Impact
Worst Case
Remote unauthenticated attacker gains root shell access on the AlienVault system, allowing complete compromise of the security monitoring infrastructure, data exfiltration, and lateral movement to other systems.
Likely Case
Attackers bypass authentication to access sensitive security data, modify alert configurations, or deploy malware on the monitoring system.
If Mitigated
With proper network segmentation and access controls, impact is limited to the AlienVault system itself, though this still represents a critical security monitoring failure.
🎯 Exploit Status
Exploit requires sending HTTP requests with specific User-Agent header. Multiple public advisories and proof-of-concepts exist.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 5.3.1
Vendor Advisory: https://www.alienvault.com/forums/discussion/7765/alienvault-v5-3-1-hotfix
Restart Required: Yes
Instructions:
1. Backup current configuration. 2. Apply AlienVault 5.3.1 hotfix or upgrade to version 5.3.1. 3. Restart AlienVault services. 4. Verify fix by checking version and testing authentication.
🔧 Temporary Workarounds
Network Access Restriction
linuxRestrict network access to AlienVault web interface to trusted IP addresses only
iptables -A INPUT -p tcp --dport 443 -s TRUSTED_IP -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP
Web Server Header Filtering
linuxConfigure web server to reject requests with 'AV Report Scheduler' in User-Agent header
Add to Apache config: SetEnvIf User-Agent "AV Report Scheduler" bad_agent
Order allow,deny
Allow from all
Deny from env=bad_agent
🧯 If You Can't Patch
- Isolate AlienVault system on separate VLAN with strict firewall rules
- Implement web application firewall (WAF) to block malicious User-Agent headers
🔍 How to Verify
Check if Vulnerable:
Check if version is below 5.3.1: cat /etc/ossim/ossim_setup.conf | grep versionCheck Version:
cat /etc/ossim/ossim_setup.conf | grep versionVerify Fix Applied:
Verify version is 5.3.1 or higher and test authentication bypass with known exploit payload📡 Detection & Monitoring
Log Indicators:
- HTTP requests with 'AV Report Scheduler' in User-Agent header
- Unauthenticated access to privileged endpoints
- Unusual process execution as root user
Network Indicators:
- HTTP traffic to AlienVault web interface with suspicious User-Agent headers
- Unexpected outbound connections from AlienVault system
SIEM Query:
source="alienvault" AND (user_agent="*AV Report Scheduler*" OR action="authentication_bypass")🔗 References
- http://www.securityfocus.com/archive/1/540224/100/0/threaded
- http://www.zerodayinitiative.com/advisories/ZDI-16-517/
- https://www.alienvault.com/forums/discussion/7765/alienvault-v5-3-1-hotfix
- http://www.securityfocus.com/archive/1/540224/100/0/threaded
- http://www.zerodayinitiative.com/advisories/ZDI-16-517/
- https://www.alienvault.com/forums/discussion/7765/alienvault-v5-3-1-hotfix
