A flaw was found in the offline_access scope in Keycloak. This issue would affect users of shared computers more (especially if cookies are not cleared), due to a lack of root session validation, and the reuse of session ids across root and user authentication sessions. This enables an attacker to resolve a user session attached to a previously authenticated user; when utilizing the refresh token, they will be issued a token for the original user.

Affected: Maven: org.keycloak:keycloak-parent

An issue was discovered in Keycloak when using a client with the `offline_access` scope. Reuse of session ids across root and user authentication sessions and a lack of root session validation enabled attackers to resolve a user session attached to a different previously authenticated user.

This issue most affects users of shared computers. Suppose a user logs out of their account (without clearing their cookies) in a mobile app or similar client that includes the `offline_access` scope, and another user authenticates to the application. In that case, it will share the same root session id, and when utilizing the refresh token, they will be issued a token for the original user.

keycloak: path traversal via double URL encoding keycloak: Session takeover with OIDC offline refreshtokens

Ein entfernter, authentisierter Angreifer kann eine Schwachstelle in Keycloak ausnutzen, um Sicherheitsvorkehrungen zu umgehen.