Is CVE-2026-36603 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-36603 being exploited in the wild.

How severe is CVE-2026-36603?

Informational severity, with a CVSS score of 8.1, published 3 June 2026.

Which products and versions are affected?

Mercusys AC12G AC12G(EU)_V1_200909, AC12G(EU)_V1_210128.

Is there a fix for CVE-2026-36603?

No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

How is CVE-2026-36603 attacked?

It is attacked from the adjacent network, in a network appliance.

Am I affected by CVE-2026-36603?

Check whether you run Mercusys AC12G at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-36603: Mercusys AC12G missing authentication for UPnP IGD actions

CVE-2026-36603 · Severity: info · CVSS 8.1 · Published 2026-06-03

The Mercusys AC12G router contains a security flaw in its UPnP service, which is used to automatically configure network settings. An attacker or a compromised device on the local network can use this flaw to create unauthorized port forwarding rules, potentially exposing internal devices to the internet. Additionally, they can disconnect the router from the internet or view sensitive network statistics without needing a password.

Technologies: Mercusys AC12G. Vendors: Mercusys.

Quick answers

Is CVE-2026-36603 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-36603 being exploited in the wild.
How severe is CVE-2026-36603?: Informational severity, with a CVSS score of 8.1, published 3 June 2026.
Which products and versions are affected?: Mercusys AC12G AC12G(EU)_V1_200909, AC12G(EU)_V1_210128.
Is there a fix for CVE-2026-36603?: No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is CVE-2026-36603 attacked?: It is attacked from the adjacent network, in a network appliance.
Am I affected by CVE-2026-36603?: Check whether you run Mercusys AC12G at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

The Mercusys AC12G (EU) V1 router's UPnP IGD (Internet Gateway Device) implementation on port 1900 exposes 15 out of 18 SOAP actions without authentication. This vulnerability (CWE-306) allows any unauthenticated device on the local area network (LAN) to execute sensitive commands such as AddPortMapping, DeletePortMapping, and ForceTermination. Attackers can exploit this to create arbitrary NAT port forwarding rules, potentially exposing internal services to the WAN, or to perform a denial-of-service by terminating the WAN connection. The service also leaks sensitive information including the WAN IP address and traffic statistics (CWE-200). The product is reportedly end-of-life, and no official patch is expected.

Affected products

Mercusys AC12G (EU) V1 AC12G(EU)_V1_200909, AC12G(EU)_V1_210128

Timeline

2026-06-03: advisory: NVD publication date
2026-06-03: disclosed: Public disclosure via GitHub advisory

References

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

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