It is identified a format string vulnerability in ASUS RT-AX56U V2 & RT-AC86U. This vulnerability is caused by directly using input as a format string when calling syslog in logmessage_normal function, in the do_detwan_cgi module of httpd. An unauthenticated remote attacker without privilege can exploit this vulnerability to perform remote arbitrary code execution, arbitrary system operation or disrupt service.This issue affects RT-AX56U V2: 3.0.0.4.386_50460; RT-AC86U: 3.0.0.4_386_51529.