CVE-2021-25811: Mercusys Mercury x18g Firmware

High severity, CVSS 7.5. EPSS: 1.6% chance of exploitation in the next 30 days.

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.

Affected products

• Mercusys Mercury x18g Firmware: version 1.0.5 only

Published 2021-04-29. Last modified 2026-06-17.