Multiple vulnerabilities have been documented for the DSL-2750U series that directly impact firmware versions earlier than 2021/2022. If your J1 device is running older firmware, it may be susceptible to the following:
Check the device info status page to confirm that the Firmware Version matches the new file you uploaded.
Index of /pub/ADSL/DSL-2750U/Firmware. This firmware is only compatible with hardware revision С. Please take a look at string "H/ D-Link FTP Wireless N ADSL2+ WI-FI Router DSL-2750U - D-Link d-link dsl-2750u h w ver j1 firmware
Follow these steps exactly. Do not skip any.
Download the latest available firmware (e.g., v1.05 or higher). This firmware is only compatible with hardware revision С
This comprehensive guide outlines how to identify your exact hardware revision, find the correct firmware binary file, and safely execute the flashing process. Why Firmware Updates for H/W Ver J1 Matter
The dynamic drivers embedded into the revised firmware file offer expanded support for modern LTE and 4G USB dongles configured in failover cellular mode via the physical USB 2.0 rear slot. Step-by-Step Firmware Flashing Protocol Download the latest available firmware (e
Complete Firmware Update Guide for D-Link DSL-2750U (Hardware Version J1)
If the router is stuck with flashing lights, it may need a factory reset. Find the small "Reset" button on the back, hold it down for 10 seconds while the device is powered on, then release it.