Serial-to-IP converter devices contain thousands of unpatched vulnerabilities that operators and defenders often overlook. These devices translate legacy industrial equipment communications into Internet Protocol, creating a bridge between air-gapped operational technology networks and connected systems. Researchers have documented both old and newly discovered flaws across multiple manufacturers. Threat actors increasingly target this class of device because they sit at critical network junctures and receive minimal security attention compared to firewalls or servers. Organizations deploying serial-to-IP converters rarely apply patches or conduct vulnerability assessments. The devices frequently run outdated firmware with no update mechanism. This combination makes them reliable entry points for attackers seeking access to industrial control systems, SCADA networks, and manufacturing environments. Defenders should inventory all serial-to-IP devices on their networks, document firmware versions, and restrict network access through segmentation. Manufacturers have released patches for known issues, but adoption remains low. Organizations should prioritize these devices in patch management workflows and treat them with the same security rigor applied to firewalls and routers rather than dismissing them as legacy pass-through hardware.