In strongSwan before 5.9.5, a malicious responder can send an EAP-Success message too early without actually authenticating the client and (in the case of EAP methods with mutual authentication and EAP-only authentication for IKEv2) even without server authentication.
https://www.strongswan.org/blog/2022/01/24/strongswan-vulnerability-%28cve-2021-45079%29.html