If you cannot get a patched firmware, replace the device. A $50 router from a reputable brand (or a community-supported OpenWrt device) is far cheaper than the cost of a ransomware attack or identity theft that starts with a compromised edge router.
Exploits allowing attackers to read /etc/passwd or configuration files, revealing user passwords or ISP authentication details. Anatomy of an Exploit: How Attacks Occur zte f680 exploit
An MD5 hash of this combined string is generated to produce a raw 128-bit key. If you cannot get a patched firmware, replace the device