strongSwan versions 4.5.0 prior to 6.0.5 contain an integer underflow vulnerability in the EAP-TTLS AVP parser that allows unauthenticated remote attackers to cause a denial of service by sending crafted AVP data with invalid length fields during IKEv2 authentication. Attackers can exploit the failure to validate AVP length fields before subtraction to trigger excessive memory allocation or NULL pointer dereference, crashing the charon IKE daemon.

strongSwan versions 5.9.2 through 5.9.5 are affected by authorization bypass through improper validation of certificate with host mismatch (CWE-297). When certificates are used to authenticate clients in TLS-based EAP methods, the IKE or EAP identity supplied by a client is not enforced to be contained in the client's certificate. So clients can authenticate with any trusted certificate and claim an arbitrary IKE/EAP identity as their own. This is problematic if the identity is used to make policy decisions. A fix was released in strongSwan version 5.9.6 in August 2022 (e4b4aabc4996fc61c37deab7858d07bc4d220136).