GMS-2024-51: keycloak-core: open redirect via "form_post.jwt" JARM response mode

January 23, 2024

An incomplete fix was found in Keycloak Core patch. An attacker can steal authorization codes or tokens from clients using a wildcard in the JARM response mode “form_post.jwt”. It is observed that changing the response_mode parameter in the original proof of concept from “form_post” to “form_post.jwt” can bypass the security patch implemented to address CVE-2023-6134.

References

github.com/advisories/GHSA-9vm7-v8wj-3fqw
github.com/keycloak/keycloak/security/advisories/GHSA-9vm7-v8wj-3fqw

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