De link
CVE-2014-0160 (OpenSSL advisory) 7th April 2014: 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 (a.k.a. Heartbleed). This issue did not affect versions of OpenSSL prior to 1.0.1. Reported by Neel Mehta. Fixed in OpenSSL 1.0.1g (Affected 1.0.1f, 1.0.1e, 1.0.1d, 1.0.1c, 1.0.1b, 1.0.1a, 1.0.1)
Eu acredito que isso é bastante autoexplicativo.