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Vulnerability record · CVE-2026-36603 · published 3 June 2026

CVE-2026-36603: Missing authentication for critical function vulnerability

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.

8.1 CVSS 3.1 High EPSS 0.33% · top 76.7% CWE-306 · Missing authentication for critical function Deferred
8.1CVSS 3.1 base score
0.33%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
1References
22 Jul 2026Last modified by NVD

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.

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

References

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

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Source: NIST National Vulnerability Database (record CVE-2026-36603), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.