CVE-2026-36603
Unauthenticated UPnP on Mercusys AC12G enables arbitrary port forwarding.
Is CVE-2026-36603 being exploited?
Not confirmed. CVE-2026-36603 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.21% probability of exploitation in the next 30 days.
How severe is CVE-2026-36603?
CVE-2026-36603 is rated High with a CVSS score of 8.1. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-36603?
Yes. A fix has been recorded for CVE-2026-36603. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-36603 affect?
CVE-2026-36603 affects Mercusys AC12G router (EU) with firmware AC12G(EU)_V1_200909. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-36603?
Update firmware or disable UPnP
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Unauthenticated LAN device can create port mappings and view WAN stats, enabling traffic redirection or data exposure.
Immediate action required