Integer underflow in OpenSSL before 0.9.8x 1.0.0 before 1.0.0j and 1.0.1 before 1.0.1c when TLS 1.1 TLS 1.2 or DTLS is used with CBC encryption allows remote attackers to cause a denial of service (buffer over-read) or possibly have unspecified other impact via a crafted TLS packet that is not properly handled during a certain explicit IV calculation.