CVE-2024-20252: Cisco Expressway CSRF Vulnerability

CVE-2024-20252 Overview

Multiple vulnerabilities in Cisco Expressway Series and Cisco TelePresence Video Communication Server (VCS) could allow an unauthenticated, remote attacker to conduct cross-site request forgery (CSRF) attacks that perform arbitrary actions on an affected device. "Cisco Expressway Series" refers to Cisco Expressway Control (Expressway-C) devices and Cisco Expressway Edge (Expressway-E) devices. An attacker could exploit this vulnerability by persuading an authenticated user to click a malicious link, potentially resulting in unauthorized configuration changes or administrative actions.

Critical Impact

Successful exploitation allows unauthenticated remote attackers to perform arbitrary administrative actions on affected Cisco Expressway and TelePresence VCS devices through CSRF attacks, potentially compromising video communication infrastructure security.

Affected Products

• Cisco Expressway Series (Expressway-C and Expressway-E)
• Cisco TelePresence Video Communication Server (VCS)
• Cisco Expressway Control and Edge devices

Discovery Timeline

• 2024-02-07 - CVE-2024-20252 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2024-20252

Vulnerability Analysis

This Cross-Site Request Forgery (CSRF) vulnerability (CWE-352) affects the web management interface of Cisco Expressway Series and TelePresence VCS devices. The vulnerability exists due to insufficient CSRF protections in the affected systems, allowing attackers to craft malicious requests that could be executed in the context of an authenticated administrator's session.

The attack requires user interaction - specifically, an authenticated administrator must be tricked into clicking a malicious link or visiting a compromised webpage while having an active session with the vulnerable device. Upon successful exploitation, the attacker can perform any administrative action that the victim user is authorized to perform, including modifying device configurations, creating or deleting user accounts, and potentially disrupting video communication services.

Root Cause

The underlying cause of this vulnerability is the lack of proper CSRF token validation in the web-based management interface. The affected devices fail to adequately verify that requests submitted to the management interface are legitimate and intentional actions from authenticated users. This missing validation allows attackers to forge requests that appear to originate from authorized administrators.

Attack Vector

The attack is network-based and requires no prior authentication to initiate. An attacker would craft a malicious web page or link containing forged HTTP requests targeting the vulnerable Cisco Expressway or TelePresence VCS device. When an authenticated administrator with an active session visits the attacker-controlled content, the malicious requests are automatically submitted to the management interface using the victim's credentials and session context.

The exploitation flow typically involves:

1. Attacker identifies a target Cisco Expressway or TelePresence VCS installation
2. Attacker crafts malicious HTML/JavaScript containing forged requests for administrative actions
3. Attacker delivers the malicious content to an administrator via phishing, compromised websites, or other social engineering techniques
4. When the administrator with an active management session accesses the malicious content, the forged requests execute with their privileges
5. Administrative actions are performed without the user's explicit consent

For detailed technical information about exploitation mechanics, refer to the Cisco Security Advisory.

Detection Methods for CVE-2024-20252

Indicators of Compromise

• Unexpected configuration changes on Cisco Expressway or TelePresence VCS devices
• Administrative actions logged without corresponding administrator awareness or intent
• Unusual HTTP requests to the management interface originating from external referrers
• User account modifications or creations that administrators did not initiate

Detection Strategies

• Monitor web server access logs for HTTP requests to administrative endpoints with suspicious or external Referer headers
• Implement alerting on configuration changes to Cisco Expressway and TelePresence VCS devices
• Review authentication logs for administrative sessions followed by unusual activity patterns
• Deploy web application firewalls (WAF) with CSRF detection capabilities in front of management interfaces

Monitoring Recommendations

• Enable comprehensive logging on Cisco Expressway and TelePresence VCS management interfaces
• Implement real-time alerting for administrative actions, especially account modifications and configuration changes
• Configure SIEM rules to correlate user sessions with originating IP addresses and detect anomalous patterns
• Monitor for outbound connections from administrator workstations to unknown or suspicious domains

How to Mitigate CVE-2024-20252

Immediate Actions Required

• Apply the security patches provided by Cisco immediately
• Restrict management interface access to trusted networks only
• Implement network segmentation to isolate management interfaces from general user traffic
• Educate administrators about phishing risks and the importance of not clicking unknown links while logged into management consoles
• Consider implementing additional authentication factors for administrative access

Patch Information

Cisco has released security updates to address this vulnerability. Organizations should review the Cisco Security Advisory (cisco-sa-expressway-csrf-KnnZDMj3) for specific patch versions and upgrade instructions. It is critical to apply the patches as soon as possible given the network-accessible nature of the vulnerability.

Workarounds

• Limit management interface access to specific trusted IP addresses using access control lists (ACLs)
• Use VPN or jump servers for all administrative access to reduce exposure
• Ensure administrators log out of management sessions when not actively in use
• Configure browser security settings to block third-party cookies and cross-origin requests where possible
• Implement network-based controls to prevent unauthorized access to management interfaces

# Example ACL configuration to restrict management access
# Limit administrative access to trusted management network only
# Configure on firewall or network device protecting the Expressway/VCS
access-list MGMT-ACCESS permit tcp 10.0.100.0/24 host 192.168.1.100 eq 443
access-list MGMT-ACCESS deny tcp any host 192.168.1.100 eq 443