CVE-2021-40350
📋 TL;DR
CVE-2021-40350 is an authentication bypass vulnerability in Christie Digital DWU850-GS projectors that allows attackers to perform any administrative action without valid credentials. Attackers can exploit this by sending crafted HTTP requests with a specific Cookie header that the device fails to validate. Organizations using affected Christie projectors in their AV/display systems are at risk.
💻 Affected Systems
- Christie Digital DWU850-GS
📦 What is this software?
Dwu850 Gs Firmware by Christiedigital
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of projector functionality including remote code execution, configuration changes, service disruption, and potential pivot point to internal networks.
Likely Case
Unauthorized control of projector settings, display manipulation, service disruption, and potential data exposure from connected systems.
If Mitigated
Limited impact with proper network segmentation and access controls preventing external exploitation.
🎯 Exploit Status
Exploitation requires sending HTTP requests with crafted Cookie header to web interface. No authentication needed.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: V06.47 or later
Vendor Advisory: https://www.christiedigital.com/support/security-advisories
Restart Required: Yes
Instructions:
1. Contact Christie Digital support for firmware update. 2. Download latest firmware version. 3. Upload firmware via projector web interface. 4. Apply update and restart device.
🔧 Temporary Workarounds
Network Segmentation
allIsolate projector network from untrusted networks and internet
Access Control Lists
linuxRestrict network access to projector management interface
iptables -A INPUT -p tcp --dport 80 -s trusted_ip -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
🧯 If You Can't Patch
- Place projector on isolated VLAN with strict firewall rules
- Disable network management interface if not required
🔍 How to Verify
Check if Vulnerable:
Check firmware version via web interface or serial console. If version is V06.46, device is vulnerable.Check Version:
curl -s http://projector-ip/version.cgi or check web interface System Information pageVerify Fix Applied:
Verify firmware version is V06.47 or later and test authentication requirements for administrative functions.📡 Detection & Monitoring
Log Indicators:
- Unauthorized access attempts to webctrl.cgi.elf
- Administrative actions from unexpected IP addresses
- Failed authentication followed by successful administrative actions
Network Indicators:
- HTTP requests to webctrl.cgi.elf with crafted Cookie headers
- Administrative API calls without prior authentication
SIEM Query:
source="projector_logs" AND (uri="*webctrl.cgi*" AND NOT user_agent="*browser*") OR (status=200 AND uri="*admin*" AND NOT auth_success=true)