Double free vulnerability in GnuTLS before 3.3.17 and 3.4.x before 3.4.4 allows remote attackers to cause a denial of service via a long DistinguishedName (DN) entry in a certificate.

GnuTLS before 2.9.10 does not verify the activation and expiration dates of CA certificates, which allows man-in-the-middle attackers to spoof servers via a certificate issued by a CA certificate that is (1) not yet valid or (2) no longer valid.

GnuTLS before 3.1.0 does not verify that the RSA PKCS #1 signature algorithm matches the signature algorithm in the certificate, which allows remote attackers to conduct downgrade attacks via unspecified vectors.

The authentication hook (mgs_hook_authz) in mod-gnutls 0.5.10 and earlier does not validate client certificates when "GnuTLSClientVerify require" is set, which allows remote attackers to spoof clients via a crafted certificate.

The _gnutls_ecc_ansi_x963_export function in gnutls_ecc.c in GnuTLS 3.x before 3.1.28, 3.2.x before 3.2.20, and 3.3.x before 3.3.10 allows remote attackers to cause a denial of service (out-of-bounds write) via a crafted (1) Elliptic Curve Cryptography (ECC) certificate or (2) certificate signing requests (CSR), related to generating key IDs.

The gnutls_x509_dn_oid_name function in lib/x509/common.c in GnuTLS 3.0 before 3.1.20 and 3.2.x before 3.2.10 allows remote attackers to cause a denial of service (NULL pointer dereference) via a crafted X.509 certificate, related to a missing LDAP description for an OID when printing the DN.

The asn1_get_bit_der function in GNU Libtasn1 before 3.6 does not properly report an error when a negative bit length is identified, which allows context-dependent attackers to cause out-of-bounds access via crafted ASN.1 data.

Multiple unspecified vulnerabilities in the DER decoder in GNU Libtasn1 before 3.6, as used in GnuTLS, allow remote attackers to cause a denial of service (out-of-bounds read) via crafted ASN.1 data.

The (1) asn1_read_value_type and (2) asn1_read_value functions in GNU Libtasn1 before 3.6 allows context-dependent attackers to cause a denial of service (NULL pointer dereference and crash) via a NULL value in an ivalue argument.

Buffer overflow in the read_server_hello function in lib/gnutls_handshake.c in GnuTLS before 3.1.25, 3.2.x before 3.2.15, and 3.3.x before 3.3.4 allows remote servers to cause a denial of service (memory corruption) or possibly execute arbitrary code via a long session id in a ServerHello message.