A flaw exists in the org.keycloak.broker.oidc package where the OIDC broker incorrectly synchronizes the emailverified claim. When an OIDC identity provider is configured with trustEmail=true and the userinfo endpoint is enabled, Keycloak retrieves the email address from the userinfo response but retrieves the emailverified status exclusively from the idtoken. The root cause is a lack of validation ensuring that the emailverified claim in the idtoken actually refers to the email address returned by the userinfo endpoint. If these two sources return different email addresses, the idtoken's emailverified=true claim is blindly applied to the userinfo email. Exploitation Conditions: The OIDC identity provider must have trustEmail set to true (non-default).

The userinfo endpoint must be enabled (default).

The attacker must control or have compromised the upstream OIDC provider.

Concrete Impact: Mark arbitrary email addresses as verified in the Keycloak database.

Bypass email-based security controls or verification workflows.

Potential account takeover if the application relies solely on the emailverified flag from the IdP to link accounts.