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.

strongSwan 4.5.x through 5.2.x before 5.2.1 allows remote attackers to cause a denial of service (invalid pointer dereference) via a crafted IKEv2 Key Exchange (KE) message with Diffie-Hellman (DH) group 1025.

strongSwan before 5.1.2 allows remote attackers to cause a denial of service (NULL pointer dereference and IKE daemon crash) via a crafted ID_DER_ASN1_DN ID payload.

IKEv2 in strongSwan 4.0.7 before 5.1.3 allows remote attackers to bypass authentication by rekeying an IKE_SA during (1) initiation or (2) re-authentication, which triggers the IKE_SA state to be set to established.

strongSwan 5.0.2 through 5.1.0 allows remote attackers to cause a denial of service (NULL pointer dereference and charon daemon crash) via a crafted IKEv1 fragmentation packet.

The compare_dn 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 ID_DER_ASN1_DN ID, related to an "insufficient length check" during identity comparison.

The is_asn1 function in strongSwan 4.1.11 through 5.0.4 does not properly validate the return value of the asn1_length function, which allows remote attackers to cause a denial of service (segmentation fault) via a (1) XAuth username, (2) EAP identity, or (3) PEM encoded file that starts with a 0x04, 0x30, or 0x31 character followed by an ASN.1 length value that triggers an integer overflow.