Keycloak Dynamic Client Registration Secret Exposure

Executive Summary

This vulnerability is in Keycloak's Dynamic Client Registration service. A user with the view-clients role can access a client registration endpoint and retrieve the client's confidential secret in cleartext. This happens because the service fails to mask sensitive information. The attacker can then use this secret to gain full access to the client's account and potentially escalate their privileges within the realm.

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Detection Guidance

To detect this vulnerability, check Keycloak logs for unauthorized access to the Dynamic Client Registration endpoint /realms/{realm}/clients-registrations/default/{clientId}. Look for requests made by users with the view-clients role that return client secrets in cleartext. Use network monitoring tools to inspect HTTP responses from this endpoint for exposed secrets.

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Impact Analysis

If you are an administrator with the view-clients role, an attacker could exploit this to obtain client secrets and impersonate those clients. This could lead to unauthorized access to sensitive data, privilege escalation, or full compromise of the Keycloak realm if the client has elevated permissions.

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Compliance Impact

This vulnerability could lead to unauthorized access to sensitive data, violating confidentiality requirements in GDPR and HIPAA. Exposure of client secrets may result in data breaches, triggering compliance violations, legal penalties, and reputational damage for organizations handling protected information.

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Mitigation Strategies

Immediately restrict access to the Dynamic Client Registration endpoint by removing the view-clients role from users who do not require it. Monitor and audit all access to this endpoint. Apply any available patches or updates from Keycloak once released. Consider disabling the endpoint if not in use.

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