A vulnerability was found in Duende IdentityServer 4. It has been rated as critical. The affected element is an unknown function of the file /connect/authorize of the component Token Renewal Endpoint. This manipulation of the argument id_token_hint causes improper authentication.
The identification of this vulnerability is CVE-2026-4349. It is possible to initiate the attack remotely. There is no exploit available.
The vendor was contacted early about this disclosure but did not respond in any way.
