Integer overflow in the crypt_raw method in the key-stretching implementation in jBCrypt before 0.4 makes it easier for remote attackers to determine cleartext values of password hashes via a brute-force attack against hashes associated with the maximum exponent.
The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.