CVE-2025-20331: Cisco ISE Stored XSS Vulnerability

CVE-2025-20331 Overview

CVE-2025-20331 is a stored 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, which allows an authenticated, remote attacker to inject malicious script into specific interface pages. When another user renders the affected page, arbitrary JavaScript executes in that user's browser context.

The issue is tracked under CWE-80: Improper Neutralization of Script-Related HTML Tags. Cisco published details in the Cisco Security Advisory on XSS.

Critical Impact
An attacker with a low-privileged ISE account can persist malicious script that executes in the browser of any user viewing the affected interface page, enabling session token theft and unauthorized actions in the administrator context.

Affected Products

Cisco Identity Services Engine (ISE)
Cisco Identity Services Engine Passive Identity Connector (ISE-PIC)
Web-based management interface component

Discovery Timeline

2025-08-06 - CVE-2025-20331 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-20331

Vulnerability Analysis

Cisco ISE is a policy management and access control platform used to enforce identity-based network access. Its web-based management interface accepts input across multiple configuration pages. The vulnerability exists because the interface fails to properly neutralize script-related HTML tags before storing and later rendering user-supplied input.

An authenticated attacker with a low-privileged account can inject crafted payloads into specific fields. The application stores the payload and returns it to other users without adequate output encoding. When an administrator or another user loads the affected page, the browser parses the injected content as executable script.

Successful exploitation permits the attacker to execute arbitrary JavaScript in the victim's browser session, read sensitive browser-accessible data, hijack session identifiers, or trigger authenticated actions on behalf of the victim. Because ISE governs network access policy, script execution in an administrator's session can pivot into broader identity and access impact.

Root Cause

The root cause is insufficient input validation and output encoding in the web-based management interface. Input received from lower-privileged users is persisted and later rendered without contextual sanitization, aligning with CWE-80.

Attack Vector

Exploitation requires network access to the management interface and valid credentials for at least a low-privileged account. The attacker submits a crafted request that stores a script payload within an affected field. A second user must then browse the vulnerable page (user interaction required) for the payload to fire. The scope change indicates that impact reaches components beyond the vulnerable module, such as the victim's authenticated browser session.

No verified public proof-of-concept code is available. Refer to the Cisco Security Advisory on XSS for vendor-provided technical details.

Detection Methods for CVE-2025-20331

Indicators of Compromise

Web management interface fields containing HTML or JavaScript syntax such as <script>, onerror=, onload=, or javascript: URIs.
Unexpected outbound HTTP requests from administrator browsers to attacker-controlled domains shortly after loading ISE management pages.
Session tokens or administrative cookies appearing in web server access logs from unusual referrers or user agents.
Audit log entries showing configuration changes initiated by administrator accounts that the users deny performing.

Detection Strategies

Inspect ISE application and audit logs for input submissions containing script tags, event handlers, or encoded script equivalents (for example, %3Cscript%3E).
Correlate low-privileged user activity with subsequent administrator browser anomalies to identify stored-then-triggered payload patterns.
Deploy web application firewall or reverse proxy rules that flag script-like input submitted to ISE management endpoints.

Monitoring Recommendations

Enable verbose audit logging on the ISE administrative interface and forward events to a centralized SIEM for retention and correlation.
Monitor administrator account activity, particularly configuration changes occurring immediately after viewing user-managed pages.
Alert on unexpected JavaScript errors or content security policy violations reported by administrator browsers accessing ISE.

How to Mitigate CVE-2025-20331

Immediate Actions Required

Apply the fixed software release identified in the Cisco Security Advisory on XSS.
Restrict management-interface access to a dedicated administrative network segment or jump-host infrastructure.
Review and reduce accounts with access to the ISE administrative UI, enforcing least privilege for operator-level roles.
Rotate administrator session credentials and invalidate active sessions after patching to remove any resident stored payloads' effect on live sessions.

Patch Information

Cisco has released fixed software for Cisco ISE and Cisco ISE-PIC. Consult the Cisco Security Advisory on XSS for the specific fixed versions and upgrade guidance. No workarounds are typically provided for Cisco XSS advisories; upgrade is required.

Workarounds

Limit administrative interface reachability to trusted management IP addresses via network access control lists.
Require multi-factor authentication for all ISE administrative accounts to raise the cost of credential-based abuse.
Audit and remove unused low-privileged accounts that could serve as the entry point for injection.
Use a dedicated browser profile for ISE administration to reduce cookie and token exposure across sessions.

bash

# Example: restrict ISE admin interface access via ACL (illustrative)
ip access-list extended ISE-ADMIN-ACCESS
 permit tcp 10.10.20.0 0.0.0.255 host <ISE_ADMIN_IP> eq 443
 deny   tcp any host <ISE_ADMIN_IP> eq 443 log
 permit ip any any