Vulnerability Exchange Formats - CycloneDX, SPDX, VDR, and VEX
Modern software is made up of a massive, interconnected web of components, with applications relying heavily on open-source libraries, third-party dependencies, and complex supply chains. This complexity creates challenges for organizations looking to track the software that’s deployed across their networks, as well as to prioritize and remediate vulnerabilities embedded within.
Understanding, prioritizing, and remediating modern vulnerabilities is far too complicated to accomplish via spreadsheets or other disconnected, manual workflows. Most organizations of any size benefit greatly from integrating and automating as much of the process as possible. In this article we’ll explore a number of standard machine-readable data formats for vulnerability data, how they are used, and how they interact to automate and improve security across the software supply chain.
Software Bill of Materials (SBOM)
A Software Bill of Materials, or SBOM, serves as the foundation for understanding the components within a piece of software. SBOMs provide the "ingredient list" of an application by enumerating all libraries, dependencies, and modules, giving organizations critical visibility into their software supply chain. This transparency enables them to identify risks, track vulnerabilities, and ensure compliance with licensing requirements. SBOMs are designed to work with automated tools, thanks to their machine-readable formats. Two leading SBOM standards, CycloneDX and SPDX, are widely used.
CycloneDX: A Security-Focused SBOM Format
CycloneDX was developed by OWASP, a global non-profit organization dedicated to improving security of web applications and other software. This SBOM standard was specifically designed with security in mind, making it a powerful tool for tracking vulnerabilities and dependencies. CycloneDX supports machine-readable formats such as JSON and XML, which enable easy integration into automated security workflows.
One of CycloneDX’s key strengths is its detailed support for dependency relationships. It not only lists software components, but also maps how they depend on each other, making it easier to assess the ripple effects of a vulnerability. For example, if a deeply nested dependency in your software stack is affected by a critical vulnerability, CycloneDX’s structure ensures this risk is surfaced clearly.
Additionally, CycloneDX has been widely adopted in DevSecOps pipelines, where it helps organizations improve security at the earliest stages in the software development lifecycle. By generating SBOMs during the development process, teams can identify vulnerable modules before software is deployed.
Software Package Data Exchange (SPDX): A Flexible and Open SBOM Standard
The Linux Foundation maintains SPDX (Software Package Data Exchange), an international open standard originally created to manage software license compliance. Over time, it has evolved into a comprehensive SBOM standard used for both licensing and security purposes. One of SPDX’s greatest strengths is its flexibility: it supports multiple formats, including JSON, YAML, RDF, and tag/value, making it highly adaptable to a variety of environments.
SPDX has been embraced by open-source projects and enterprises alike. It is especially valuable for organizations managing large software ecosystems with diverse licensing requirements. Its compatibility with automated tools ensures that security and compliance checks can scale with the complexity of modern applications.
Vulnerability Disclosure Reports (VDR)
When a new vulnerability is confirmed in a piece of software or hardware, it’s important to communicate it quickly and clearly to the broader community so defenders can take action. A Vulnerability Disclosure Report (VDR) formalizes this process, offering essential details such as the nature of the vulnerability, the affected systems or software versions, and remediation steps.
VDRs are typically published by vendors or service providers alongside the relevant SBOM for their product and its dependencies, and is updated over time as new vulnerabilities emerge. A VDR for a piece of software captures known vulnerabilities that affect it, along with descriptions and suggested plans for addressing them, in a machine-readable format. Incorporating VDRs into vulnerability management processes allows security teams to quickly understand and manage their baseline exposure.
Vulnerability Exploitability Exchange (VEX)
Not all vulnerabilities are equally dangerous, and not all require immediate action. The Vulnerability Exploitability Exchange (VEX) standard addresses this by answering a critical question: Is a given vulnerability exploitable in a specific environment? While an SBOM and VDR can help to identify vulnerabilities present within a system, a VEX report provides the context needed to prioritize remediation efforts.
VEX reports are structured to map vulnerabilities to specific configurations or deployment scenarios. For instance, a vulnerability might exist in a library but be rendered non-exploitable because the affected feature is not used in the application, or due to environmental conditions. By providing this clarity, VEX reports help organizations focus their resources on risks that matter most.
Bringing It All Together
SBOMs, VDRs, and VEX reports address different but interconnected stages of the vulnerability management lifecycle, forming a cohesive framework for identifying, analyzing, and prioritizing software vulnerabilities. Together, they provide a robust system for understanding risks and responding effectively.
Consider a scenario like the Log4j vulnerability (CVE-2021-44228). When the vulnerability was disclosed, security teams relied on VDRs for detailed information about its impact and affected versions of software they had deployed in their organizations. With an SBOM in hand, organizations could autonomously identify whether their applications included a vulnerable library, either directly or as a nested dependency.
For those affected, correlating with VEX reports provided crucial insights into whether the vulnerability was exploitable, immediately highlighting the applications that were at most risk, and in the most need of remediation. Together, these standards enable a streamlined, automated approach to managing vulnerabilities, reducing the time between discovery and resolution.
Standards Help Build Resilience Through Automation
In an era where vulnerability exploits are rapidly on the rise, SBOMs, VDRs, and VEX reports are indispensable tools for streamlining vulnerability management. Their machine-readable nature enables automation, driving scalable and effective vulnerability management even in large and complex environments. By adopting and integrating these formats into their vulnerability management workflows, organizations can strengthen their security posture, reduce risk, and build resilience against ever-evolving threats.