|OpenSSL before 0.9.8za, 1.0.0 before 1.0.0m, and 1.0.1 before 1.0.1h
does not properly restrict processing of ChangeCipherSpec messages,
which allows man-in-the-middle attackers to trigger use of a
zero-length master key in certain OpenSSL-to-OpenSSL communications,
and consequently hijack sessions or obtain sensitive information, via
a crafted TLS handshake, aka the "CCS Injection" vulnerability.