For more information, refer to the official advisory: OpenSSL Security Advisory [07 Apr 2014]

TLS heartbeat read overrun (CVE-2014-0160)
==========================================

A missing bounds check in the handling of the TLS heartbeat extension can be
used to reveal up to 64KB of memory to a connected client or server.

Only 1.0.1 and 1.0.2-beta releases of OpenSSL are affected, including
1.0.1f and 1.0.2-beta1.

Thanks to Neel Mehta of Google Security for finding this bug and to
Adam Langley <agl@chromium.org> and Bodo Moeller <bmoeller@acm.org> for
preparing the fix.

Affected users should upgrade to OpenSSL 1.0.1g. Users unable to immediately
upgrade can alternatively recompile OpenSSL with -DOPENSSL_NO_HEARTBEATS.

1.0.2 is also fixed in 1.0.2-beta2.