CVE-2026-36603

Name: CVE-2026-36603
Creator: NVD / NIST
Published: 2026-06-03T18:16:21.29+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 8.1/10EPSS 0.21%

Last modified Jun 17, 2026

CVE-2026-36603 is a high-severity vulnerability rated 8.1/10 on the CVSS scale. 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.. EPSS estimates a 0.21% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

8.1/10

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

EPSS Probability

0.21%

11.4th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-306

References

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

Timeline

Published: Jun 3, 2026
Last Modified: Jun 17, 2026
Status: Deferred

Frequently Asked Questions

What is CVE-2026-36603?

How severe is CVE-2026-36603?

CVE-2026-36603 has a CVSS score of 8.1/10 (HIGH severity). The EPSS model estimates a 0.21% probability of exploitation in the next 30 days.

How do I fix CVE-2026-36603?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2026-36603?

Run a free Strix scan to check your systems for this vulnerability.

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Source: NVD / NIST