Executive brief
Keycloak, a tool used for managing user identities and logins, has a security flaw in how it handles certain login requests. If a system is configured with broad redirect rules, an attacker can trick the system into sending a user's login information to the wrong place. This could result in a user being logged into an account controlled by the attacker, potentially leading to unauthorized access or session swapping.
Technical details
A HTTP Parameter Pollution (HPP) vulnerability exists in the org.keycloak.protocol.saml package of Keycloak. The flaw occurs because the SAML HTTP-Redirect binding response preserves the full query string from the initial authentication request. If a client is configured with a wildcard redirect URI, an attacker can craft an AuthnRequest with an AssertionConsumerServiceURL containing pre-filled SAMLResponse and RelayState parameters. Keycloak then appends its legitimate parameters to the URL, resulting in duplicates. Service providers that prioritize the first occurrence of a query parameter may process the attacker's data instead of the legitimate response, enabling session swapping or login CSRF.
Affected products
- Red Hat Red Hat Build of Keycloak All versions
- Keycloak Keycloak All versions
Timeline
- 2026-07-29: disclosed: Reported via Red Hat Bugzilla
- 2026-07-31: advisory: NVD and Red Hat advisory published