Parse Server missing audience validation in Keycloak authentication adapter

Impact

The Keycloak authentication adapter does not validate the azp (authorized party) claim of Keycloak access tokens against the configured client-id. A valid access token issued by the same Keycloak realm for a different client application can be used to authenticate as any user on the Parse Server that uses the Keycloak adapter. This enables cross-application account takeover in multi-client Keycloak realms.

All Parse Server deployments that use the Keycloak authentication adapter with a Keycloak realm that has multiple client applications are affected.

Patches

The fix replaces the userinfo HTTP call with local JWT verification and enforces azp claim validation against the configured client-id.

Workarounds

None.

References

• GitHub security advisory: https://github.com/parse-community/parse-server/security/advisories/GHSA-48mh-j4p5-7j9v
• Fix Parse Server 9: https://github.com/parse-community/parse-server/releases/tag/9.5.2-alpha.5
• Fix Parse Server 8: https://github.com/parse-community/parse-server/releases/tag/8.6.18