DUHK vulnerability (Dont Use Hard-coded Keys) is the last cryptographic implementation vulnerability that could be exploited by attackers to recover encryption keys used to secure VPN connections and web browsing sessions. The vulnerability affects devices using the ANSI X9.31 Random Number Generator (RNG) in conjunction with a hard-coded seed key. The problem is related to the fact that Pseudorandom number generators are not able to generate random numbers and knowledge of initial secret value (seed) could be used to determine the number generated by the algorithm.”]
Source: https://securityaffairs.co/wordpress/64725/hacking/duhk-attack.html