CVE-2025-20304: Cisco Identity Services Engine XSS Flaw

CVE-2025-20304 Overview

CVE-2025-20304 is a reflected Cross-Site Scripting (XSS) vulnerability in the web-based management interface of Cisco Identity Services Engine (ISE) and Cisco ISE Passive Identity Connector (ISE-PIC). The flaw stems from insufficient validation of user-supplied input in specific pages of the management interface. An authenticated, remote attacker with a low-privileged account can inject malicious script that executes in another user's browser session. Successful exploitation can allow arbitrary script execution in the interface context or exposure of sensitive browser-based information.

Critical Impact
An authenticated attacker with low privileges can execute arbitrary JavaScript in an administrator's browser session, enabling session data theft, UI manipulation, and pivot into privileged ISE workflows.

Affected Products

Cisco Identity Services Engine 3.2 (base through Patch 7)
Cisco Identity Services Engine 3.3 (base through Patch 7)
Cisco Identity Services Engine 3.4 (base through Patch 3)

Discovery Timeline

2025-11-05 - CVE-2025-20304 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-20304

Vulnerability Analysis

The vulnerability is a reflected XSS issue [CWE-79] in the Cisco ISE and ISE-PIC administrative web interface. The affected pages accept user-controlled parameters and render them back to the response without adequate output encoding or input sanitization. When a victim loads a crafted URL or interacts with an attacker-influenced page, the injected script executes within the victim's authenticated session context.

Exploitation requires two conditions. First, the attacker must hold at least a low-privileged account on the target ISE deployment. Second, an authenticated user must be induced to trigger the malicious request. Because the ISE management plane governs network access policy, identity services, and posture, script execution in an administrator context can be leveraged to read sensitive data or issue actions on behalf of the victim.

Root Cause

The root cause is improper neutralization of input during web page generation. Specific interface pages reflect request parameters into the rendered HTML without contextual escaping, allowing HTML and JavaScript payloads to break out of intended data contexts and execute in the browser.

Attack Vector

The attack vector is network-based and requires user interaction. An authenticated low-privileged attacker crafts a URL or form submission containing a malicious script payload targeting a vulnerable ISE management page. When a higher-privileged user follows the link while authenticated, the payload executes in their browser under the ISE origin, exposing session cookies, tokens, or DOM-accessible data. No verified public proof-of-concept is available. See the Cisco Security Advisory for vendor details.

Detection Methods for CVE-2025-20304

Indicators of Compromise

HTTP requests to ISE administrative endpoints containing script tags, javascript: URIs, or common XSS payload markers such as onerror=, onload=, or encoded angle brackets in query parameters.
Unexpected outbound requests from administrator browsers to attacker-controlled domains shortly after interacting with ISE URLs.
Administrative sessions performing unusual sequences of API calls immediately after page loads containing suspicious query strings.

Detection Strategies

Inspect ISE web server access logs for parameter values containing HTML entities, <script, %3Cscript, or event handler attributes.
Correlate low-privileged account activity that generates URLs subsequently accessed by administrator accounts.
Deploy WAF or reverse proxy rules that flag reflected input patterns on ISE management endpoints.

Monitoring Recommendations

Enable verbose HTTP request logging on ISE nodes and forward logs to a centralized analytics platform for signature and anomaly review.
Alert on administrator sessions originating actions immediately after loading URLs with encoded script fragments.
Monitor for creation, modification, or export of ISE policy objects performed within seconds of a suspicious page load.

How to Mitigate CVE-2025-20304

Immediate Actions Required

Upgrade Cisco ISE and ISE-PIC to a fixed release as identified in the Cisco Security Advisory cisco-sa-ise-multiple-vulns-O9BESWJH.
Restrict access to the ISE administrative interface to a dedicated management network and trusted jump hosts.
Review and reduce low-privileged account membership on ISE, removing accounts that no longer require access.
Instruct administrators to avoid clicking untrusted links while authenticated to the ISE management console.

Patch Information

Cisco has published fixed software for affected 3.2, 3.3, and 3.4 branches. Refer to the Cisco Security Advisory cisco-sa-ise-multiple-vulns-O9BESWJH for the specific fixed patch levels applicable to each release train, and apply the corresponding patch to all ISE and ISE-PIC nodes.

Workarounds

No vendor workaround is documented; applying the fixed patch is the recommended remediation.
Enforce browser isolation or dedicated management browsers for ISE administration to limit blast radius of script execution.
Implement network-level ACLs limiting management interface reachability to a small set of trusted operator workstations.

bash

# Example ACL restricting ISE admin interface (TCP/443) to a management subnet
ip access-list extended ISE-ADMIN-ACCESS
 permit tcp 10.10.20.0 0.0.0.255 host <ISE_MGMT_IP> eq 443
 deny   tcp any host <ISE_MGMT_IP> eq 443 log
 permit ip any any