Asus is undoubtedly affected among the manufacturers, but there may be easily hackable routers among many OEM products.
Security experts at Tenable and Juniper Networks warn that routers that use control software developed by Arcadyan or Buffalo may have a critical security flaw. The vulnerability basically affects older models released in the last couple of years, and the list may grow as investigations progress, but it is already over 20. Security flaws are constantly surfacing, but hackers are actively exploiting the current vulnerability, so anyone using one of the affected routers is no longer safe.
The researchers found a case where, after hacking the router, the Mirai malware was remotely installed on the device and used to set up a botnet. This botnet network was then used to launch DDoS attacks against certain service providers to cripple their websites by causing overloads. The exact list of routers affected by the vulnerability can be checked at https://www.tenable.com/security/research/tra-2021-13.
Users of affected routers can hope that the manufacturers will provide an update to fix the bug soon.