An issue was discovered in cookie encryption in phpMyAdmin. The decryption of the username/password is vulnerable to a padding oracle attack. This can allow an attacker who has access to a user's browser cookie file to decrypt the username and password.

Furthermore, the same initialization vector (IV) is used to hash the username and password stored in the phpMyAdmin cookie. If a user has the same password as their username, an attacker who examines the browser cookie can see that they are the same - but the attacker can not directly decode these values from the cookie as it is still hashed. All 4.6.x versions (prior to 4.6.4), 4.4.x versions (prior to 4.4.15.8), and 4.0.x versions (prior to 4.0.10.17) are affected.