CVE-2025-20204: Cisco Identity Services Engine XSS Flaw

CVE-2025-20204 Overview

A stored cross-site scripting (XSS) vulnerability exists in the web-based management interface of Cisco Identity Services Engine (ISE). This vulnerability allows an authenticated, remote attacker with administrative privileges to inject malicious code into specific pages of the interface. The vulnerability stems from insufficient validation of user-supplied input by the web-based management interface, which can lead to arbitrary script code execution in the context of the affected interface or unauthorized access to sensitive browser-based information.

Critical Impact

Authenticated attackers can inject malicious scripts that execute in other administrators' browsers, potentially stealing session tokens, capturing credentials, or performing unauthorized administrative actions on behalf of legitimate users.

Affected Products

• Cisco Identity Services Engine 3.2.0 (including Patch 1 through Patch 7)
• Cisco Identity Services Engine 3.3.0 (including Patch 1 and Patch 2)
• Cisco Identity Services Engine 3.4.0

Discovery Timeline

• February 5, 2025 - CVE-2025-20204 published to NVD
• March 28, 2025 - Last updated in NVD database

Technical Details for CVE-2025-20204

Vulnerability Analysis

This vulnerability is classified as CWE-79 (Improper Neutralization of Input During Web Page Generation), commonly known as Cross-Site Scripting. The flaw resides in the web-based management interface of Cisco ISE, where user-supplied input is not properly validated or sanitized before being rendered in the browser context.

When an administrator with valid credentials injects malicious JavaScript code into specific pages of the interface, the payload is stored on the server and subsequently executed whenever another user views the affected page. This stored XSS variant is particularly dangerous because it persists across sessions and can affect multiple users without requiring direct attacker interaction for each victim.

The attack requires high privileges (administrative credentials) but can impact other administrators who access the compromised pages. The scope is changed, meaning the vulnerable component and impacted component are different—the vulnerable component is the ISE management interface, while the impacted component is the victim's browser session.

Root Cause

The root cause is insufficient input validation and output encoding in the Cisco ISE web-based management interface. The application fails to properly sanitize user-controlled data before storing it in the database and subsequently rendering it in HTML responses. This allows attackers to inject JavaScript code that bypasses security controls and executes in the browser context of other users.

Attack Vector

The attack vector is network-based and requires the attacker to have valid administrative credentials to the Cisco ISE management interface. The exploitation flow involves:

1. An attacker authenticates to the Cisco ISE web management interface using valid administrative credentials
2. The attacker navigates to a vulnerable page that accepts user input
3. Malicious JavaScript code is injected into an input field that lacks proper validation
4. The payload is stored in the ISE database
5. When another administrator views the affected page, the malicious script executes in their browser context
6. The attacker can then steal session cookies, capture keystrokes, redirect users to malicious sites, or perform administrative actions on behalf of the victim

The vulnerability requires user interaction—a victim must visit the page containing the injected payload for the attack to succeed.

Detection Methods for CVE-2025-20204

Indicators of Compromise

• Unusual JavaScript code or HTML tags appearing in ISE management interface pages
• Unexpected HTTP requests to external domains originating from administrator sessions
• Modified or suspicious entries in ISE configuration pages or user-editable fields
• Administrator accounts reporting unexpected behavior or unauthorized changes

Detection Strategies

• Implement web application firewall (WAF) rules to detect XSS payloads in requests to ISE management interfaces
• Enable verbose logging on Cisco ISE to capture all administrative actions and input submissions
• Monitor network traffic for outbound connections from ISE administrator sessions to unknown external hosts
• Conduct regular security audits of ISE configuration pages to identify injected content

Monitoring Recommendations

• Review Cisco ISE audit logs for suspicious administrative activities or unusual input patterns
• Configure SIEM alerts for potential XSS attack signatures in HTTP traffic to ISE management interface
• Implement Content Security Policy (CSP) reporting to detect script execution anomalies
• Monitor for session hijacking indicators such as concurrent sessions from different IP addresses

How to Mitigate CVE-2025-20204

Immediate Actions Required

• Apply the security patches provided by Cisco as described in the official security advisory
• Limit administrative access to Cisco ISE management interface to trusted users only
• Implement network segmentation to restrict access to ISE management ports
• Enable multi-factor authentication (MFA) for all administrative accounts to reduce credential compromise risk

Patch Information

Cisco has released security updates to address this vulnerability. Organizations should consult the Cisco Security Advisory for specific patch versions and upgrade instructions. Affected versions include Cisco ISE 3.2.0 through 3.2.0 Patch 7, 3.3.0 through 3.3.0 Patch 2, and 3.4.0. Organizations should upgrade to the fixed software versions as specified in the advisory.

Workarounds

• Restrict administrative access to the ISE management interface to specific trusted IP addresses using access control lists
• Implement browser-based XSS protection by ensuring administrators use modern browsers with built-in XSS filters enabled
• Disable or limit access to vulnerable pages if they are not essential for operations until patches can be applied
• Consider deploying a reverse proxy with XSS filtering capabilities in front of the ISE management interface

# Example access control configuration to restrict management interface access
# Configure ACL on network devices to limit ISE admin access
access-list 101 permit tcp host 192.168.1.10 host 10.0.0.1 eq 443
access-list 101 permit tcp host 192.168.1.11 host 10.0.0.1 eq 443
access-list 101 deny tcp any host 10.0.0.1 eq 443