OpenSSL < 1.1.0 Default Weak 64-bit Block Cipher (SWEET32)
Medium Nessus Plugin ID 93112
SynopsisThe service running on the remote host uses a weak encryption block cipher by default.
DescriptionAccording to its banner, the version of OpenSSL running on the remote host is prior to 1.1.0. It is, therefore, affected by a vulnerability, known as SWEET32, in the 3DES and Blowfish algorithms due to the use of weak 64-bit block ciphers by default. A man-in-the-middle attacker who has sufficient resources can exploit this vulnerability, via a 'birthday' attack, to detect a collision that leaks the XOR between the fixed secret and a known plaintext, allowing the disclosure of the secret text, such as secure HTTPS cookies, and possibly resulting in the hijacking of an authenticated session.
SolutionUpgrade to OpenSSL version 1.1.0 or later, and ensure all 64-bit block ciphers are disabled. Note that upgrading to OpenSSL 1.1.0 does not completely mitigate this vulnerability; it simply disables the vulnerable 64-bit block ciphers by default.