The comparedn function in utils/identification.c in strongSwan 4.3.3 through 5.1.1 allows (1) remote attackers to cause a denial of service (out-of-bounds read, NULL pointer dereference, and daemon crash) or (2) remote authenticated users to impersonate arbitrary users and bypass access restrictions via a crafted IDDERASN1DN ID, related to an "insufficient length check" during identity comparison.

The GMP Plugin in strongSwan 4.2.0 through 4.6.3 allows remote attackers to bypass authentication via a (1) empty or (2) zeroed RSA signature, aka "RSA signature verification vulnerability."

The server implementation of the EAP-MSCHAPv2 protocol in the eap-mschapv2 plugin in strongSwan 4.2.12 through 5.x before 5.3.4 does not properly validate local state, which allows remote attackers to bypass authentication via an empty Success message in response to an initial Challenge message.

strongSwan 4.3.0 through 5.x before 5.3.2 and strongSwan VPN Client before 1.4.6, when using EAP or pre-shared keys for authenticating an IKEv2 connection, does not enforce server authentication restrictions until the entire authentication process is complete, which allows remote servers to obtain credentials by using a valid certificate and then reading the responses.