CVE-2025-20304 identifies multiple reflected Cross-Site Scripting (XSS) vulnerabilities in the web-based management interface of Cisco Identity Services Engine (ISE) and Cisco ISE-PIC. These vulnerabilities arise from insufficient validation and improper neutralization of user-supplied input during web page generation. An attacker with at least low-level authenticated access can craft malicious input that, when reflected in specific interface pages, executes arbitrary JavaScript code in the context of the victim user's browser session. This can lead to unauthorized actions such as session hijacking, theft of sensitive information stored in the browser, or manipulation of the management interface. The vulnerability affects a wide range of Cisco ISE versions from 3.1.0 through 3.4 Patch 3, covering multiple patches and minor releases. The CVSS v3.1 base score is 5.4 (medium), reflecting network attack vector, low attack complexity, low privileges required, and user interaction needed. The scope is changed (S:C), indicating that exploitation can affect resources beyond the vulnerable component. No public exploits have been reported to date. The vulnerability primarily threatens confidentiality and integrity of the management interface sessions but does not impact system availability. Cisco ISE is widely used for network access control, policy enforcement, and identity management, making this vulnerability significant in environments relying on centralized network security controls.

For European organizations, the exploitation of this vulnerability could lead to unauthorized disclosure of sensitive information accessible via the Cisco ISE management interface, including session tokens or administrative data. Attackers could leverage this to escalate privileges or manipulate network access policies, potentially undermining network security posture. Given Cisco ISE's role in enforcing network access control and policy compliance, a successful attack could facilitate lateral movement or unauthorized network access within corporate or critical infrastructure environments. Although the vulnerability requires authenticated access and user interaction, insider threats or compromised low-privilege accounts could be leveraged. The impact is particularly critical in sectors with stringent regulatory requirements such as finance, healthcare, and government, where data confidentiality and integrity are paramount. Disruption of network access control policies could also indirectly affect operational continuity. The absence of known exploits reduces immediate risk but does not eliminate the threat, especially as attackers often develop exploits post-disclosure.

European organizations should immediately assess their Cisco ISE deployments to identify affected versions and prioritize patching to the latest fixed releases once available. In the interim, implement strict input validation and sanitization controls on the management interface to prevent injection of malicious scripts. Restrict access to the Cisco ISE management interface to trusted networks and enforce multi-factor authentication (MFA) to reduce the risk of compromised credentials. Monitor user activity logs for unusual behavior indicative of exploitation attempts. Employ Content Security Policy (CSP) headers to limit the execution of unauthorized scripts in browsers accessing the interface. Regularly review and minimize user privileges, ensuring that only necessary personnel have access to the management interface. Conduct security awareness training to reduce the risk of social engineering attacks that could facilitate user interaction required for exploitation. Network segmentation and isolation of management interfaces can further reduce exposure. Finally, maintain up-to-date backups and incident response plans tailored to identity and access management systems.