In verify_emsa_pkcs1_signature() in gmp_rsa_public_key.c in the gmp plugin in strongSwan 4.x and 5.x before 5.7.0, the RSA implementation based on GMP does not reject excess data after the encoded algorithm OID during PKCS#1 v1.5 signature verification. Similar to the flaw in the same version of strongSwan regarding digestAlgorithm.parameters, a remote attacker can forge signatures when small public exponents are being used, which could lead to impersonation when only an RSA signature is used for IKEv2 authentication.

strongSwan 5.6.0 and older allows Remote Denial of Service because of Missing Initialization of a Variable.

In stroke_socket.c in strongSwan before 5.6.3, a missing packet length check could allow a buffer underflow, which may lead to resource exhaustion and denial of service while reading from the socket.

The rsa_pss_params_parse function in libstrongswan/credentials/keys/signature_params.c in strongSwan 5.6.1 allows remote attackers to cause a denial of service via a crafted RSASSA-PSS signature that lacks a mask generation function parameter.

strongSwan 5.2.2 and 5.3.0 allows remote attackers to cause a denial of service (daemon crash) or execute arbitrary code.

The gmp plugin in strongSwan before 5.6.0 allows remote attackers to cause a denial of service (NULL pointer dereference and daemon crash) via a crafted RSA signature.

The ASN.1 parser in strongSwan before 5.5.3 improperly handles CHOICE types when the x509 plugin is enabled, which allows remote attackers to cause a denial of service (infinite loop) via a crafted certificate.

The gmp plugin in strongSwan before 5.5.3 does not properly validate RSA public keys before calling mpz_powm_sec, which allows remote peers to cause a denial of service (floating point exception and process crash) via a crafted certificate.

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.