CVE-2026-36603 | BDVDB-2026-337455 Detail

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.

Impact#

Per CVSS v3.1: confidentiality impact high, integrity impact high, availability impact none. Attack vector: adjacent.

Weaknesses#

CWE-306 Missing Authentication for Critical Function

References#

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

Exploit#

No public exploit known

History#

Version 12026-06-03Record published in the CVE List.
Version 22026-06-05Most recent update recorded in the CVE List.

Published

Published: 2026-06-03
Last modified: 2026-06-05

Vendor information

Vendor: Not stated
Product: Not stated

Score

8.1 High

EPSS

less than 1%, Very Low

Estimated chance of exploitation in the next 30 days. EPSS percentile: 11.4.

KEV

Not listed in the CISA Known Exploited Vulnerabilities catalog.

Impact

Authentication Issues

Action

No specific action is recorded in the source data. Check the references for vendor guidance.

Affected Systems

No version data in the source record.

Scoring System

CVSS v4.0

Not available

CVSS v3.1

8.1 High

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

Metric breakdown
Attack Vector	Adjacent
Attack Complexity	Low
Privileges Required	None
User Interaction	None
Scope	Unchanged
Confidentiality	High
Integrity	High
Availability	None

CVSS v3.0

Not available

CVSS v2

Not available

Source: CVE List v5 (record); CISA KEV (kev, action); FIRST EPSS (epss).