CVE-2025-20303: Cisco Identity Services Engine XSS Vulnerability

CVE-2025-20303 Overview

CVE-2025-20303 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). An authenticated remote attacker with a low-privileged account can inject malicious script into specific pages of the interface. Successful exploitation executes arbitrary script code in the browser context of another user or exposes sensitive browser-based information. The flaw is classified under [CWE-79] and stems from insufficient validation of user-supplied input.

Critical Impact
Authenticated attackers can hijack administrator sessions, steal cookies, or perform actions in the context of higher-privileged ISE users after tricking them into loading a crafted URL.

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-2025-20303 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-20303

Vulnerability Analysis

The vulnerability resides in the web-based management interface of Cisco ISE and ISE-PIC. Multiple input parameters on specific interface pages fail to sanitize or encode user-supplied data before reflecting it into HTTP responses. An authenticated attacker crafts a request containing JavaScript payloads embedded in vulnerable parameters. When a targeted user, typically an administrator, loads the attacker-supplied link, the browser executes the injected script inside the ISE web session context.

Because ISE is a policy decision point for network access control, session compromise on the management interface can lead to broader impact. An attacker can pivot from stolen session tokens to modify authentication, authorization, and accounting (AAA) policies or exfiltrate configuration data visible through the console.

Root Cause

The root cause is improper neutralization of input during web page generation [CWE-79]. The affected pages echo attacker-controlled parameters into the HTML response without contextual output encoding or input validation, allowing HTML and JavaScript to be interpreted by the victim's browser.

Attack Vector

Exploitation requires network reachability to the ISE management interface and valid credentials for at least a low-privileged account. The attack also requires user interaction: a higher-privileged user must click a crafted link or visit an attacker-controlled page that issues the request. The scope is changed because script execution occurs in the victim's authenticated browser context, affecting resources beyond the attacker's own privileges. No verified public exploit or proof-of-concept has been published for this issue.

Refer to the Cisco Security Advisory on Multiple Vulnerabilities for the list of affected parameters and pages.

Detection Methods for CVE-2025-20303

Indicators of Compromise

HTTP requests to the ISE management interface containing script tags, javascript: URIs, event handlers such as onerror= or onload=, or encoded variants in query parameters.
Administrator sessions originating from unexpected geographies or user agents shortly after a low-privileged user accessed the interface.
Unexpected outbound requests from administrator browsers to unknown domains following ISE console usage.

Detection Strategies

Inspect web server and application logs on ISE for reflected parameter values containing HTML metacharacters (<, >, ", ') or common XSS keywords.
Deploy a web application firewall (WAF) or reverse proxy in front of the management interface with XSS signatures enabled for detection and blocking.
Correlate low-privileged account activity with subsequent administrator session anomalies in SIEM data.

Monitoring Recommendations

Forward ISE administrative and audit logs to a centralized SIEM and alert on suspicious parameter content and admin session changes.
Monitor the ISE management interface for repeated 4xx/5xx responses tied to malformed input patterns typical of XSS probing.
Track and review all low-privileged administrative accounts, revoking dormant or unnecessary access.

How to Mitigate CVE-2025-20303

Immediate Actions Required

Apply the fixed Cisco ISE and ISE-PIC releases listed in the Cisco Security Advisory.
Restrict access to the ISE management interface to a dedicated administrative network or jump host.
Audit all administrative and low-privileged accounts on ISE and remove those no longer required.

Patch Information

Cisco has released fixed software addressing this issue in ISE 3.2, 3.3, and 3.4 branches. Upgrade to a patched release identified in the vendor advisory. There is no evidence of exploitation in the wild, and this CVE is not listed in the CISA Known Exploited Vulnerabilities catalog.

Workarounds

Limit management interface reachability to trusted administrative subnets using access control lists.
Require administrators to use dedicated privileged access workstations that do not browse untrusted content.
Enforce short session timeouts and re-authentication for sensitive ISE actions to reduce the window for session abuse.

bash

# Example: restrict ISE admin interface to a management subnet on an upstream ACL
access-list ISE_MGMT permit tcp 10.10.50.0 0.0.0.255 host <ISE_MGMT_IP> eq 443
access-list ISE_MGMT deny   tcp any host <ISE_MGMT_IP> eq 443
access-list ISE_MGMT permit ip any any