A flaw exists in the org.keycloak.broker.oidc package where the OIDC broker incorrectly synchronizes the email_verified 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 email_verified status exclusively from the id_token. The root cause is a lack of validation ensuring that the email_verified claim in the id_token actually refers to the email address returned by the userinfo endpoint. If these two sources return different email addresses, the id_tokens email_verified=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 email_verified flag from the IdP to link accounts.
Weakness
The product receives a complex input with multiple elements or fields that must be consistent with each other, but it does not validate or incorrectly validates that the input is actually consistent.
Extended Description
Some input data can be structured with multiple elements or fields that must be consistent with each other, e.g. a number-of-items field that is followed by the expected number of elements. When such complex inputs are inconsistent, attackers could trigger unexpected errors, cause incorrect actions to take place, or exploit latent vulnerabilities.
Potential Mitigations
- Assume all input is malicious. Use an “accept known good” input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
- When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, “boat” may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as “red” or “blue.”
- Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code’s environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.