A PRNG's output is not truly random; it's a predictable sequence determined entirely by its initial seed. If an attacker can observe some of the generator's output, they can launch a brute-force attack by systematically trying every possible seed value until they find the one that produces the matching sequence. Once the seed is discovered, the attacker can predict every future number the PRNG will generate, completely breaking its security. This risk is directly tied to the size of the seed space. A small seed space—like one using a 16-bit integer (65,536 possibilities) instead of a cryptographically secure 256-bit seed—drastically reduces the number of guesses an attacker needs to make. Modern computing power can exhaust such small spaces quickly, rendering the PRNG useless for security-sensitive operations like generating encryption keys, session tokens, or authentication codes.