Many security protocols can sustain attacks against vulnerabilities introduced either in the protocol design (specification), implementation, and even configuration stages (in which different, viable protocol options are set). For example, researchers found while testing a ZigBee-based consumer IoT implementation that the protocol was designed for easy setup and usage but lacked configuration possibilities for security and performed vulnerable device pairing procedures. These procedures allow external parties to sniff the exchanged network key during the ZigBee pairing transaction and gain control of the ZigBee device. Understanding the limitations of a chosen protocol is absolutely critical to determining what additional layered security controls must be put in place to keep the system secure (https://www.blackhat.com/docs/us-15/materials/us-15-Zillner-ZigBee-Exploited-The-Good-The-Bad-And-The-Ugly-wp.pdf).

Massively deployed, too, is the WPA2 (Wi-Fi protected access) cryptographic protocol built into almost every home and business wireless router. In late 2017, this protocol was found, by security researcher, Mathy Vanhoef, to be vulnerable to a class of attack called a key reinstallation attack, wherein the attacker forces the device (in this case, in perfect accordance with the standardized protocol) to reuse a cryptographic key (see https://www.krackattacks.com). Given the ubiquity of 802.11, millions of devices needed to be patched for the vulnerability and many remain vulnerable to this day. The attack allows the victim's traffic to be decrypted by the attacker; injection of malicious traffic into the network is also feasible.