CVE-2025-20331 is a medium-severity stored Cross-Site Scripting (XSS) vulnerability affecting multiple versions of Cisco Identity Services Engine (ISE) software, including versions 2.7.0 p8 through 3.4.0 and various patches thereof. The vulnerability exists in the web-based management interface of Cisco ISE and Cisco ISE-PIC, where insufficient validation of user-supplied input allows an authenticated attacker with at least low-privileged access to inject malicious script code into specific pages of the interface. When other users access these pages, the injected scripts execute in the context of the victim’s browser session, potentially exposing sensitive browser-based information or enabling further attacks such as session hijacking or privilege escalation within the management interface. The vulnerability requires authentication and user interaction (viewing the malicious page) to be exploited. The CVSS 3.1 base score is 5.4, reflecting network attack vector, low attack complexity, low privileges required, and user interaction needed, with impacts on confidentiality and integrity but no impact on availability. No known exploits are currently reported in the wild. This vulnerability highlights the risk of stored XSS in critical network management platforms, where attackers with limited access can leverage scripting flaws to compromise administrative sessions or extract sensitive data from the management console.

For European organizations, the impact of this vulnerability can be significant, especially for enterprises and service providers relying on Cisco ISE for network access control, policy enforcement, and identity management. Successful exploitation could lead to unauthorized disclosure of sensitive configuration data, session hijacking of privileged users, or manipulation of network access policies, undermining network security and compliance efforts. Given that Cisco ISE is widely deployed in large corporate and governmental networks across Europe, exploitation could facilitate lateral movement within networks or enable attackers to bypass security controls. The requirement for low-privileged authentication reduces the attack surface but does not eliminate risk, as insider threats or compromised user credentials could be leveraged. The vulnerability does not directly impact availability, but the confidentiality and integrity impacts could lead to significant operational disruptions and regulatory consequences under GDPR if sensitive personal or organizational data is exposed.

To mitigate this vulnerability, European organizations should prioritize the following actions: 1) Apply Cisco’s security patches or updates for Cisco ISE as soon as they become available, ensuring all affected versions are updated to a fixed release. 2) Enforce strict access controls and multi-factor authentication (MFA) for all users accessing the Cisco ISE management interface to reduce the risk of credential compromise and unauthorized access. 3) Conduct regular audits of user accounts and privileges to minimize the number of low-privileged users who can access the interface. 4) Implement Content Security Policy (CSP) headers and other browser-based security controls where possible to limit the impact of injected scripts. 5) Monitor Cisco ISE logs and network traffic for unusual activities indicative of exploitation attempts, such as unexpected script injections or anomalous user behavior. 6) Train administrators and users on phishing and social engineering risks that could lead to credential theft, which would facilitate exploitation. 7) Segment the management interface network to restrict access only to trusted hosts and administrators, reducing exposure to remote attackers. These targeted measures go beyond generic advice by focusing on reducing the likelihood of authenticated access by attackers and limiting the impact of potential script injection.