CWE-1209 Failure to Disable Reserved Bits

The reserved bits in a hardware design are not disabled prior to production.

• Confidentiality, Integrity, Availability, Access Control, Accountability, Authentication, Authorization, Non-Repudiation: Varies by Context — If the logic being controlled by these bits is still enabled in production, an adversary could use the logic to induce unwanted/unsupported behavior in the hardware. Adversaries with access to these bits will write to them in hopes of compromising hardware state. This type of weakness all depends on the capabilities of the logic being controlled or configured by the reserved bits.

• [Architecture and Design, Implementation] Include a feature to disable reserved bits. • [Integration] Any writes to these reserve bits are blocked (e.g., ignored, access-protected, etc.), or an exception can be asserted.