CVE-2023-6291

Ein entfernter, anonymer oder authentisierter Angreifer kann mehrere Schwachstellen in Keycloak ausnutzen, um Sicherheitsvorkehrungen zu umgehen oder einen Denial of Service zu verursachen.

An issue was found in the redirect_uri validation logic that allows for a bypass of otherwise explicitly allowed hosts. The problem arises in the verifyRedirectUri method, which attempts to enforce rules on user-controllable input, but essentially causes a desynchronization in how Keycloak and browsers interpret URLs. Keycloak, for example, receives "[www%2ekeycloak%2eorg%2fapp%2f:y@example.com](https://www%2ekeycloak%2eorg%2fapp%2f:y@example.com/)" and thinks the authority to be keycloak.org when it is actually example.com. This happens because the validation logic is performed on a URL decoded version, which no longer represents the original input. ### Acknowledgements Karel Knibbe