CVE-2024-20405: Cisco Finesse Stored XSS Vulnerability

CVE-2024-20405 Overview

A vulnerability in the web-based management interface of Cisco Finesse could allow an unauthenticated, remote attacker to conduct a stored cross-site scripting (XSS) attack by exploiting a Remote File Inclusion (RFI) vulnerability. This vulnerability is due to insufficient validation of user-supplied input for specific HTTP requests that are sent to an affected device.

An attacker could exploit this vulnerability by persuading a user to click a crafted link. A successful exploit could allow the attacker to execute arbitrary script code in the context of the affected interface or access sensitive information on the affected device.

Critical Impact

Unauthenticated remote attackers can execute arbitrary JavaScript in authenticated user sessions, potentially leading to session hijacking, credential theft, and unauthorized access to sensitive contact center data.

Affected Products

• Cisco Finesse 11.6(1) and all ES versions (ES4 through ES8)
• Cisco Finesse 12.6(2) and ES versions (ES01, ES02)
• All versions of Cisco Finesse prior to the patched releases

Discovery Timeline

• June 5, 2024 - CVE-2024-20405 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2024-20405

Vulnerability Analysis

This vulnerability combines two distinct attack techniques: Remote File Inclusion (RFI) and Stored Cross-Site Scripting (XSS). The web-based management interface of Cisco Finesse fails to properly validate and sanitize user-supplied input for specific HTTP requests. This weakness allows attackers to include remotely hosted malicious content that gets stored and subsequently executed when other users access the affected interface.

The vulnerability is classified under CWE-20 (Improper Input Validation) and CWE-79 (Improper Neutralization of Input During Web Page Generation), indicating that the core issue stems from inadequate input sanitization routines in the application's request handling logic.

Because the vulnerability can be exploited by unauthenticated attackers but requires user interaction (clicking a crafted link), it represents a significant risk to organizations using Cisco Finesse for contact center operations where sensitive customer data may be accessible through the interface.

Root Cause

The root cause of CVE-2024-20405 is insufficient validation of user-supplied input for specific HTTP requests sent to the Cisco Finesse web-based management interface. The application fails to properly sanitize external URLs and script content before storing and rendering them, allowing malicious payloads to be included from remote sources and subsequently executed in users' browsers.

This improper input validation enables the RFI component to fetch external malicious content, while the lack of output encoding allows the stored XSS payload to execute when the page is rendered for subsequent users.

Attack Vector

The attack is network-based and requires user interaction. An attacker must craft a malicious link containing the RFI payload and persuade a legitimate user to click on it. The attack flow typically follows these steps:

1. The attacker identifies the vulnerable endpoint in the Cisco Finesse web management interface
2. A specially crafted HTTP request is constructed that includes a reference to a malicious remote file containing XSS payload
3. The attacker distributes the malicious link via phishing emails, social engineering, or other means
4. When a victim clicks the link, the RFI vulnerability allows the external script to be included and stored
5. The XSS payload executes in the context of the victim's authenticated session, allowing the attacker to steal session tokens, access sensitive data, or perform actions on behalf of the user

The exploitation mechanism involves the vulnerable endpoint failing to validate whether included file references point to trusted sources, combined with the absence of proper content security policies that would prevent inline script execution.

Detection Methods for CVE-2024-20405

Indicators of Compromise

• Unusual HTTP requests to the Cisco Finesse management interface containing external URL references or encoded script payloads
• Web server logs showing requests with suspicious <script> tags, javascript: URI schemes, or remote file paths
• Evidence of data exfiltration to unknown external domains from users accessing the Finesse interface
• Session anomalies indicating potential session hijacking following user access to the management interface

Detection Strategies

• Implement web application firewall (WAF) rules to detect and block requests containing RFI patterns such as external URL inclusions in user-controllable parameters
• Monitor Cisco Finesse access logs for HTTP requests with suspicious payloads including script tags, encoded JavaScript, or remote file references
• Deploy browser-based XSS detection tools and Content Security Policy (CSP) violation monitoring
• Utilize SIEM correlation rules to identify patterns of social engineering followed by anomalous Finesse interface access

Monitoring Recommendations

• Enable detailed access logging for all Cisco Finesse management interface endpoints
• Configure alerts for outbound connections from the Finesse server to unexpected external domains
• Monitor for Content Security Policy violations that may indicate XSS exploitation attempts
• Track user session patterns to identify potential session hijacking following exploitation

How to Mitigate CVE-2024-20405

Immediate Actions Required

• Apply the security patches provided by Cisco as documented in the Cisco Security Advisory
• Restrict access to the Cisco Finesse web-based management interface to trusted networks only using firewall rules
• Educate users about the risks of clicking unknown or suspicious links, particularly those appearing to target internal systems
• Enable strict Content Security Policy headers on the Finesse server if possible to mitigate XSS impact

Patch Information

Cisco has released security updates to address this vulnerability. Organizations should consult the Cisco Security Advisory for the specific patched versions applicable to their deployment. The advisory provides guidance on upgrading from affected versions including Finesse 11.6(1) and 12.6(2) series releases.

Workarounds

• Implement network segmentation to limit access to the Cisco Finesse management interface from untrusted networks
• Deploy a web application firewall (WAF) with rules to filter requests containing RFI and XSS attack patterns
• Configure browser security headers including X-XSS-Protection, X-Content-Type-Options, and strict Content-Security-Policy directives
• Use network access control lists (ACLs) to restrict management interface access to authorized administrative IP addresses only

# Example: Restrict Finesse management interface access via firewall
# Allow access only from trusted admin network
iptables -A INPUT -p tcp --dport 443 -s 10.10.10.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP