CVE-2023-20105
📋 TL;DR
This vulnerability allows authenticated remote attackers with read-only credentials to elevate privileges to administrator level on Cisco Expressway and TelePresence VCS systems. Attackers can exploit incorrect password change handling to reset any user's password, including administrators, and impersonate them. Organizations using affected Cisco video collaboration products 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 where attackers gain administrative control, reset all passwords, access sensitive data, and potentially pivot to other network resources.
Likely Case
Attackers with existing read-only access escalate to full administrative privileges, enabling configuration changes, data exfiltration, and persistence on the system.
If Mitigated
With proper network segmentation and access controls, impact is limited to the affected video collaboration system without lateral movement.
🎯 Exploit Status
Exploitation requires authenticated access but uses simple crafted web requests; read-only credentials are sufficient.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Refer to Cisco advisory for specific fixed versions
Vendor Advisory: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-expressway-priv-esc-Ls2B9t7b
Restart Required: Yes
Instructions:
1. Review Cisco advisory for fixed versions. 2. Download appropriate patches from Cisco Software Center. 3. Apply patches during maintenance window. 4. Restart affected devices. 5. Verify successful update.
🔧 Temporary Workarounds
Restrict Web Interface Access
allLimit access to the web-based management interface to trusted IP addresses only
Configure firewall rules to restrict access to Expressway/VCS management ports (typically 443/TCP)
Minimize Read-Only Accounts
allReduce number of read-only user accounts and implement strong authentication
Review and remove unnecessary read-only accounts
Implement MFA where possible
🧯 If You Can't Patch
- Implement strict network segmentation to isolate Expressway/VCS systems from critical infrastructure
- Monitor for unusual password change activities and privilege escalation attempts
🔍 How to Verify
Check if Vulnerable:
Check device version via web interface or CLI and compare against Cisco advisoryCheck Version:
From CLI: xStatus SystemUnit Software VersionVerify Fix Applied:
Verify installed version matches patched version from Cisco advisory📡 Detection & Monitoring
Log Indicators:
- Multiple password change requests from read-only users
- Administrative login from unusual IP addresses
- User privilege changes in audit logs
Network Indicators:
- Unusual web requests to password change endpoints
- Traffic from read-only accounts to administrative interfaces
SIEM Query:
source="expressway" AND (event_type="password_change" OR event_type="privilege_escalation")