CVE-2015-5211

CVE-2015-5211 is a vulnerability that affected multiple versions of the OpenSSL cryptographic software library. This flaw allowed an attacker to initiate a denial-of-service attack on a server, resulting in a complete shutdown of the targeted system. Such an attack was achieved by exploiting a weakness in the Diffie-Hellman key exchange protocol used in the OpenSSL library. The vulnerability was discovered in May 2015 and assigned the CVE identifier shortly thereafter. The exploit was discovered by security researchers who identified that the OpenSSL implementation of the Diffie-Hellman key exchange protocol was flawed, allowing an attacker to force a downgrade of the encryption protocol to a weaker level. Attackers could exploit this vulnerability by sending specially crafted network packets to the server, causing it to crash or become unresponsive. Due to its severity and widespread use of OpenSSL at the time, this vulnerability was considered critical. To address the issue, the OpenSSL project released a security advisory recommending users to upgrade their software to a patched version immediately. In addition, various organizations and vendors provided patches for their products to mitigate the vulnerability. Fortunately, even though the vulnerability was widely publicized, there were no known successful attacks in the wild before a fix was made available.