CVE-2022-20812
📋 TL;DR
This CVE describes multiple vulnerabilities in Cisco Expressway Series and TelePresence VCS that allow remote attackers to overwrite arbitrary files or conduct null byte poisoning attacks. These vulnerabilities affect the API and web-based management interface, potentially leading to system compromise. Organizations using affected Cisco video communication devices are at risk.
💻 Affected Systems
- Cisco Expressway Control (Expressway-C)
- Cisco Expressway Edge (Expressway-E)
- Cisco TelePresence Video Communication Server (VCS)
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise allowing attacker to execute arbitrary code, modify system files, disrupt services, and potentially pivot to other network resources.
Likely Case
Unauthorized file overwriting leading to service disruption, configuration changes, or data manipulation affecting video communication services.
If Mitigated
Limited impact with proper network segmentation, access controls, and monitoring in place, potentially only affecting isolated management interfaces.
🎯 Exploit Status
Exploitation requires access to management interfaces; may involve multiple steps to achieve file overwrite or null byte poisoning
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Refer to Cisco security advisories for specific fixed versions
Vendor Advisory: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-expressway-csrf-sqpsSfY6
Restart Required: Yes
Instructions:
1. Review Cisco security advisories for affected versions. 2. Download and apply the appropriate firmware update from Cisco. 3. Reboot affected devices after patching. 4. Verify patch installation and functionality.
🔧 Temporary Workarounds
Network Access Restriction
allRestrict network access to management interfaces to trusted IP addresses only
Configure firewall rules to limit access to Expressway/VCS management interfaces
Interface Disablement
allDisable unnecessary management interfaces if not required for operations
Disable web management interface if CLI/API access is sufficient
🧯 If You Can't Patch
- Implement strict network segmentation to isolate Expressway/VCS devices from untrusted networks
- Enable comprehensive logging and monitoring for unauthorized access attempts to management interfaces
🔍 How to Verify
Check if Vulnerable:
Check device firmware version against Cisco's affected versions list in security advisoriesCheck Version:
show status system (on Cisco Expressway/VCS CLI)Verify Fix Applied:
Verify firmware version has been updated to patched version specified in Cisco advisories📡 Detection & Monitoring
Log Indicators:
- Unauthorized access attempts to management interfaces
- Unexpected file modification events
- Failed authentication attempts followed by successful access
Network Indicators:
- Unusual traffic patterns to management ports
- Multiple failed API requests followed by successful ones
SIEM Query:
source="expressway*" AND (event_type="authentication_failure" OR event_type="file_modification")🔗 References
- https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-expressway-csrf-sqpsSfY6
- https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-expressway-overwrite-3buqW8LH
- https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-expressway-csrf-sqpsSfY6
- https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-expressway-overwrite-3buqW8LH
