The administrator application on ASUS GT-AC2900 devices before 3.0.0.4.386.42643 and Lyra Mini before 3.0.0.4_384_46630 allows authentication bypass when processing remote input from an unauthenticated user, leading to unauthorized access to the administrator interface. This relates to handle_request in router/httpd/httpd.c and auth_check in web_hook.o. An attacker-supplied value of '\0' matches the device's default value of '\0' in some situations. Note: All versions of Lyra Mini and earlier which are unsupported (End-of-Life, EOL) are also affected by this vulnerability, Consumers can mitigate this vulnerability by disabling the remote access features from WAN.
https://www.atredis.com/blog/2021/4/30/asus-authentication-bypass
https://www.asus.com/us/supportonly/lyra%20mini/helpdesk_bios/
https://github.com/atredispartners/advisories/blob/master/ATREDIS-2020-0010.md