CVE-2026-36603

HIGH

Mercusys AC12G (EU) V1 - Unauthenticated UPnP Port Forwarding Manipulation

Title source: llm

Description

Mercusys AC12G (EU) V1 router with firmware AC12G(EU)_V1_200909 exposes 15 of 18 UPnP IGD actions without authentication on port 1900, including AddPortMapping and GetExternalIPAddress. UPnP is enabled by default through the admin interface, allowing any unauthenticated LAN device to create arbitrary port forwarding rules and access WAN traffic statistics.

References (1)

Core 1

Core References

https://github.com/Tymbark7372/MERCUSYS-AC12G/blob/master/advisories/CVE-2026-36603.md

View Writeup ZIP pw:eip

Scores

CVSS v3 8.1

EPSS 0.0021

EPSS Percentile 11.3%

Attack Vector ADJACENT_NETWORK

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

CISA SSVC

Vulnrichment

Exploitation none

Automatable no

Technical Impact total

Details

CWE

CWE-306

Status published

Published Jun 03, 2026

Tracked Since Jun 03, 2026