An unpatched vulnerability in Calix GS7 XGS (GS5239XG) residential routers used by multiple U.S. broadband providers allows remote, unauthenticated attackers to create port-forwarding rules that can expose local network devices to the public internet.
The flaw is tracked as CVE-2026-75501 and is described as a missing authentication issue that affects devices running EXOS/6.6.47 firmware.
Security researcher Brian Khan Quintana discovered the flaw and, after trying to notify the vendor on June 7 without success, he reported the vulnerability to the Carnegie Mellon CERT Coordination Center.
Following multiple attempts to contact the vendor and receiving no response, CERT/CC coordinated a public disclosure, and Quintana published the technical details.