CVE-2023-6717 is a vulnerability identified in Keycloak, an open-source identity and access management solution widely used for single sign-on and federated identity. The flaw exists in the SAML client registration component, where an attacker with administrative privileges or client registration access can register malicious JavaScript URIs as Assertion Consumer Service (ACS) POST Binding URLs. This improper neutralization of input during web page generation leads to a Cross-Site Scripting (XSS) vulnerability. When users from different realms or applications interact with the affected forms, the malicious JavaScript executes in their browser context, potentially allowing the attacker to hijack sessions, steal credentials, or perform unauthorized actions within the Keycloak instance. The vulnerability requires high privileges (administrator or client registration rights) and user interaction (form submission) to exploit. The CVSS 3.1 score is 6.0, reflecting medium severity due to the need for privileges and user interaction, but with high impact on confidentiality and integrity and low impact on availability. No public exploits have been reported yet, but the vulnerability poses a significant risk to environments relying on Keycloak for identity federation and access control.

For European organizations, this vulnerability could lead to unauthorized access to sensitive identity and access management functions, compromising user credentials and session tokens across multiple realms and applications. This can result in data breaches, privilege escalation, and disruption of authentication services. Organizations using Keycloak in critical sectors such as finance, healthcare, government, and telecommunications may face severe operational and reputational damage. The multi-realm impact increases the attack surface, potentially affecting a broad user base. Given the central role of Keycloak in federated identity management, exploitation could undermine trust in authentication processes and lead to cascading security failures across integrated systems.

Organizations should immediately review and restrict administrative and client registration privileges to trusted personnel only, minimizing the number of users who can register SAML clients. Implement strict input validation and sanitization on ACS POST Binding URLs to prevent JavaScript URIs from being registered. Monitor Keycloak logs for suspicious client registrations or unusual administrative activities. Apply available patches or updates from Keycloak as soon as they are released. Consider deploying Web Application Firewalls (WAFs) with rules to detect and block malicious JavaScript payloads in SAML requests. Conduct regular security audits and penetration testing focused on identity management components. Educate administrators on the risks of registering untrusted clients and enforce multi-factor authentication for administrative access to reduce risk of compromised credentials.