CVE-2026-20076 is a stored cross-site scripting vulnerability found in the web-based management interface of Cisco Identity Services Engine (ISE) software. The root cause is insufficient validation and neutralization of user-supplied input during web page generation, allowing an authenticated attacker with administrative privileges to inject malicious JavaScript code into specific pages of the management interface. When other users access these pages, the injected script executes in their browser context, potentially exposing sensitive information such as session tokens or enabling further attacks like privilege escalation or session hijacking. The vulnerability affects a broad range of Cisco ISE versions from 3.1.0 up to 3.4.0, including multiple patch releases. Exploitation requires valid administrative credentials and user interaction, which limits the attack vector primarily to insider threats or compromised admin accounts. The CVSS v3.1 score of 4.8 reflects a medium severity level, with network attack vector, low attack complexity, high privileges required, and user interaction necessary. The impact primarily affects confidentiality and integrity, with no direct availability impact. No public exploits have been reported to date, but the vulnerability poses a risk to organizations relying on Cisco ISE for centralized network access control and policy management.

For European organizations, the impact of this vulnerability can be significant in environments where Cisco ISE is deployed to enforce network access policies, especially in sectors with sensitive data such as finance, healthcare, and critical infrastructure. An attacker exploiting this vulnerability could execute arbitrary scripts within the management interface, potentially leading to unauthorized disclosure of sensitive information, session hijacking, or manipulation of network policies. Given that exploitation requires administrative credentials, the risk is heightened if credential management is weak or insider threats exist. Compromise of Cisco ISE could undermine network security posture, enabling lateral movement or unauthorized access to protected resources. The vulnerability does not affect availability directly but could facilitate further attacks that degrade service or compromise network integrity. Organizations with strict regulatory requirements under GDPR must consider the confidentiality impact seriously, as data leakage through XSS could lead to compliance violations and reputational damage.

1. Apply the latest Cisco patches and updates for Cisco Identity Services Engine as soon as they become available to remediate the vulnerability. 2. Enforce strong administrative credential policies, including multi-factor authentication (MFA) for all Cisco ISE management accounts to reduce the risk of credential compromise. 3. Limit administrative access to Cisco ISE management interfaces to trusted networks and IP addresses using network segmentation and firewall rules. 4. Monitor administrative account activity and audit logs for unusual behavior that could indicate exploitation attempts or insider threats. 5. Implement Content Security Policy (CSP) headers and other web security best practices on the management interface if configurable, to reduce the impact of XSS. 6. Conduct regular security awareness training for administrators to recognize phishing and social engineering attacks that could lead to credential theft. 7. Consider deploying web application firewalls (WAF) with custom rules to detect and block malicious input patterns targeting the Cisco ISE interface. 8. Review and minimize the number of users with administrative privileges to reduce the attack surface.