CVE-2024-20255
📋 TL;DR
An unauthenticated CSRF vulnerability in Cisco Expressway Series and TelePresence VCS SOAP API allows attackers to trick authenticated users into executing unauthorized actions. This could force affected systems to reload, causing service disruption. All systems running vulnerable versions with web management interfaces exposed are at risk.
💻 Affected Systems
- Cisco Expressway Series
- Cisco TelePresence Video Communication Server (VCS)
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system reload leading to service disruption, potential configuration changes if combined with other vulnerabilities, and denial of service.
Likely Case
Temporary service interruption due to forced system reload, requiring manual intervention to restore functionality.
If Mitigated
No impact if proper CSRF protections are implemented or if management interfaces are not exposed to untrusted networks.
🎯 Exploit Status
Exploitation requires tricking an authenticated user to click a malicious link, making it dependent on social engineering.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check Cisco advisory for specific fixed versions per product
Vendor Advisory: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-expressway-csrf-KnnZDMj3
Restart Required: Yes
Instructions:
1. Review Cisco advisory for affected versions. 2. Download and apply the appropriate firmware update. 3. Reboot the system as required. 4. Verify the update was successful.
🔧 Temporary Workarounds
Restrict Management Interface Access
allLimit access to web management interface to trusted IP addresses only
Configure firewall rules to restrict access to management IP/ports
Implement CSRF Tokens
allAdd CSRF protection tokens to web interface if custom development allows
🧯 If You Can't Patch
- Implement strict network segmentation to isolate management interfaces
- Use web application firewalls (WAF) with CSRF protection rules
🔍 How to Verify
Check if Vulnerable:
Check system version against Cisco advisory. If running vulnerable version with web interface exposed, assume vulnerable.Check Version:
Check via web interface: System > Status > Software or CLI: xStatus SystemUnit SoftwareVerify Fix Applied:
Verify system version is updated to fixed release specified in Cisco advisory and test CSRF protections.📡 Detection & Monitoring
Log Indicators:
- Unexpected system reloads
- Multiple SOAP API requests from same session with different origins
- CSRF token validation failures
Network Indicators:
- HTTP POST requests to SOAP endpoints without Referer headers
- Requests with mismatched Origin/Referer headers
SIEM Query:
source="cisco-expressway" AND (event="system_reload" OR event="api_auth_failure")