Zyxel VMG5313-B30B router on firmware 5.13(ABCJ.6)b3_1127, and possibly older versions of firmware are affected by insecure permissions which allows regular and other users to create new users with elevated privileges. This is done by changing “FirstIndex” field in JSON that is POST-ed during account creation. Similar may also be possible with account deletion.
Source: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-24355
Reference (s):
- https://blog.somegeneric.ninja/Zyxel_VMG5153_B30B
- https://blog.somegeneric.ninja/Zyxel_VMG5153_B30B_part2
- https://www.zyxel.com/support/security_advisories.shtml