OpenSSL is vulnerable to a denial of service, caused by a NULL pointer dereference in signature_algorithms processing. By sending a specially crafted renegotiation ClientHello message from a client, a remote attacker could exploit this vulnerability to cause the TLS server to crash.
OpenSSL could allow a remote attacker to bypass security restrictions, caused by a missing check in the validation logic of X.509 certificate chains by the X509_V_FLAG_X509_STRICT flag. By using any valid certificate or certificate chain to sign a specially crafted certificate, an attacker could bypass the check that non-CA certificates must not be able to issue other certificates and override the default purpose.
The exploitation of these vulnerabilities could allow an attacker to use a valid non-certificate authority (CA) certificate to act as a CA and sign a certificate for an arbitrary organization, user or device, or to cause a denial of service (DoS) condition.
Refer to Cisco Security Advisory for the patch, upgrade, or suggested workaround information.