What exactly is the Heartbleed vulnerability?
On April 7, 2014, the OpenSSL community announced that it found a critical vulnerability in the TLS Heartbeat protocol. The nature of such an attack is very similar to a buffer overflow attack, where a remote attacker can exploit the protocol by sending a malformed “heartbeat” request with a payload size bigger than the actual request. In response, the vulnerable server would return a heartbeat response that contains a memory block of up to 64KB in the payload. This memory block can potentially reveal confidential information, including SSL private keys, user passwords and more. The researchers that found this vulnerability have put together an informative micro site that explains all of this.