Leveraging Common Weakness Enumeration (CWE) for Enhanced RISC-V CPU Security

When RISC-V emerged as an open-source alternative to proprietary processor architectures, it opened the door to a new era of innovation. Its flexibility and modularity have attracted widespread adoption across industries—from consumer electronics to aerospace. But alongside this opportunity lies a significant challenge: security.

Unlike software, which can be patched post-deployment, hardware vulnerabilities are far more difficult to fix once a system is fabricated. This makes early vulnerability detection a critical component of secure hardware design. And in this space, the Common Weakness Enumeration (CWE) framework, developed by MITRE, is proving to be a powerful ally—especially when combined with advanced verification tools like Cycuity's Radix.

The Security Imperative in RISC-V's Open Landscape

RISC-V’s open and customizable nature brings with it unique security concerns. As System-on-Chip (SoC) designs become more complex, spanning hardware, firmware, and software layers, the surface area for potential attacks expands. The increasing number of hardware-related Common Vulnerabilities and Exposures (CVEs) reported by NIST highlights the growing sophistication and frequency of hardware-based threats.

At the root of these threats are hardware weaknesses—design flaws or conditions that could be exploited to compromise system security. These are captured in the MITRE CWE database, while actual exploits are recorded in the CVE database. Understanding and addressing these weaknesses is crucial for building secure RISC-V systems.

MITRE’s Hardware CWE Framework: A Structured Approach

Traditionally used in software security, the CWE framework has been extended to hardware, offering a systematic way to classify and mitigate design flaws. MITRE currently lists 108 hardware-specific CWEs across 13 categories, encompassing:

• General logic design

• Memory and storage

• Cryptography

• Transient execution

• Debug and test access

This structured classification empowers hardware designers to identify and address potential weaknesses early in the design cycle. For RISC-V development, this is particularly impactful—around 65% of all hardware CWEs are applicable to RISC-V processors, with some categories seeing relevance rates exceeding 70%.

Addressing Microarchitectural Threats: New CWEs for Transient Execution

With the rise of Spectre, Meltdown, and other side-channel attacks, transient execution vulnerabilities have become a major concern. Recognizing this, MITRE introduced a new set of CWEs in early 2024, developed in collaboration with industry leaders including AMD, Intel, Arm, Cycuity, and Riscure.

Some of the key additions include:

• CWE-1421: Shared Microarchitectural State

• CWE-1422: Stale Data Forwarding

• CWE-1423: Integrity of Predictors

These weaknesses fall under CWE-1420: Exposure of Sensitive Information during Transient Execution, which is part of the broader hardware design category. These CWEs directly map to attack vectors exploited by speculative execution attacks, providing actionable insights for mitigation strategies.

From Weakness Identification to Security Verification

The value of CWEs lies not just in classification, but in how they support a traceable and verifiable security process. The CWE-based methodology allows engineers to map:

• A recognized weakness (CWE)

• To a protection requirement

• To a specific security property

• Verified through simulation, emulation, or formal methods

This structured approach ensures that security is not based on assumptions, but on provable evidence.

Cycuity’s Radix: Enabling Scalable, Architecture-Agnostic Security Verification

Cycuity, a leader in hardware security verification, plays a pivotal role in implementing this framework effectively. Their flagship product, Radix, leverages information flow analysis to track the movement of secure assets (such as encryption keys) across hardware and firmware boundaries.

Key benefits of Radix include:

• Support for early-stage vulnerability detection

• Alignment with MITRE CWE classifications

• Architecture-agnostic design, with seamless integration into RISC-V workflows

• Compatibility with simulation, emulation, and formal verification tools

• Support for firmware-in-the-loop analysis

By simulating how attackers might exploit design flaws—such as improper access control or leakage through shared microarchitectural resources—Radix helps identify vulnerabilities before the chip is even manufactured.

The Mutual Reinforcement of MITRE and RISC-V

The synergy between MITRE and RISC-V is rooted in a shared philosophy: security through openness.

• RISC-V, as an open and collaboratively developed standard, follows the principle that a system should remain secure even when its design is public.

• CWE, as a community-maintained repository, promotes transparency and consistency in the identification of weaknesses.

Together, they enable a robust, standardized approach to hardware security, allowing the semiconductor industry to build trustworthy systems from the ground up.

Conclusion: Proactive Security in the Age of Custom Silicon

As the RISC-V ecosystem continues to expand, proactive and measurable security practices must become standard in hardware development. Tools like Cycuity’s Radix, combined with the structured insight of the MITRE CWE framework, offer a practical path forward.

By identifying weaknesses early, mapping them to verifiable requirements, and incorporating analysis into the design lifecycle, engineers can secure RISC-V systems without compromising on performance or flexibility.

The future of secure hardware starts with transparency, collaboration, and the right tools. RISC-V and MITRE CWE are showing us how to get there.

Source - Semiwiki