CVE-2026-20111 is a stored cross-site scripting (XSS) vulnerability found in the web-based management interface of Cisco Prime Infrastructure, a widely used network management solution. The root cause is insufficient validation of user-supplied input fields within the interface, allowing an authenticated attacker with administrative privileges to inject malicious JavaScript code. This injected code executes in the context of the victim's browser session when they access the affected interface, potentially compromising confidentiality by stealing session tokens, cookies, or other sensitive information accessible via the browser. The vulnerability requires the attacker to have valid administrative credentials, which limits exploitation to insiders or attackers who have already compromised an admin account. The vulnerability affects an extensive list of Cisco Prime Infrastructure versions, spanning from 2.0.0 through multiple updates of 3.10.x, including various deployment packages and FIPS/FED variants. The CVSS v3.1 base score is 4.8 (medium severity), reflecting network attack vector, low attack complexity, high privileges required, user interaction needed, and partial impact on confidentiality and integrity but no impact on availability. No public exploits or active exploitation have been reported to date. The vulnerability's scope is limited to the Cisco Prime Infrastructure management interface, but given the critical role of this product in network operations, successful exploitation could lead to further compromise or data leakage within managed environments.

For European organizations, the impact of CVE-2026-20111 can be significant, especially for those relying heavily on Cisco Prime Infrastructure for managing complex network environments. An attacker exploiting this vulnerability could execute malicious scripts in the context of the management interface, potentially leading to theft of session cookies, credentials, or other sensitive data accessible via the browser. This could facilitate further lateral movement or privilege escalation within the network. Although exploitation requires administrative credentials, insider threats or credential compromise scenarios are realistic risks. The vulnerability does not directly affect network availability but can undermine the integrity and confidentiality of network management operations. Given the critical infrastructure managed by Cisco Prime Infrastructure, such as enterprise networks, service provider environments, and data centers, successful exploitation could disrupt operational security and trust. European organizations in sectors like telecommunications, finance, government, and critical infrastructure are particularly at risk due to their reliance on Cisco network management solutions.

1. Immediate application of Cisco's security updates and patches for all affected versions of Cisco Prime Infrastructure as soon as they become available. 2. Enforce strict access controls and multi-factor authentication (MFA) for all administrative accounts to reduce the risk of credential compromise. 3. Regularly audit and monitor administrative account usage and login activities to detect suspicious behavior early. 4. Implement Content Security Policy (CSP) headers and other browser security mechanisms to mitigate the impact of potential XSS attacks. 5. Limit the number of users with administrative privileges to the minimum necessary and ensure they are trained on secure usage practices. 6. Conduct periodic security assessments and penetration testing focused on the management interface to identify and remediate input validation weaknesses. 7. Use network segmentation to isolate management interfaces from general user networks, reducing exposure. 8. Employ web application firewalls (WAFs) with custom rules to detect and block malicious payloads targeting the management interface. 9. Maintain up-to-date backups and incident response plans to quickly recover from any compromise resulting from exploitation.