A hard-coded cryptographic key vulnerability exists in the user-configuration backup mechanism of TP-Link RE305 V3 and Archer C7 V5. A fixed AES-128 key and initialization vector are embedded in the firmware configuration-management component. An attacker who obtains an affected configuration backup file may extract the cryptographic material from the firmware and use it to decrypt the backup.  Successful exploitation may disclose sensitive configuration information contained in a backup file, including administrator passwords and Wi-Fi credentials.