MERCUSYS Mercury X18G 1.0.5 devices allow Denial of service via a crafted value to the POST listen_http_lan parameter. Upon subsequent device restarts after this vulnerability is exploted the device will not be able to access the webserver unless the listen_http_lan parameter to uhttpd.json is manually fixed.
https://cve.mitre.org/cgi-bin/cvename.cgi?name=cve-2021-25811