Posted by Oliver Chang and Andrew Pollock, Google Open Source Security Team

It is an interesting time for everyone concerned with open source vulnerabilities. The U.S. Executive Order on Improving the Nation’s Cybersecurity requirements for vulnerability disclosure programs and assurances for software used by the US government will go into effect later this year. Finding and fixing security vulnerabilities has never been more important, yet with increasing interest in the area, the vulnerability management space has become fragmented—there are a lot of new tools and competing standards.

In 2021, we announced the launch of OSV, a database of open source vulnerabilities built partially from vulnerabilities found through Google’s OSS-Fuzz program. OSV has grown since then and now includes a widely adopted OpenSSF schema and a vulnerability scanner. In this blog post, we’ll cover how these tools help maintainers track vulnerabilities from discovery to remediation, and how to use OSV together with other SBOM and VEX standards.

Vulnerability Databases

The lifecycle of a known vulnerability begins when it is discovered. To reach developers, the vulnerability needs to be added to a database. CVEs are the industry standard for describing vulnerabilities across all software, but there was a lack of an open source centric database. As a result, several independent vulnerability databases exist across different ecosystems.

To address this, we announced the OSV Schema to unify open source vulnerability databases. The schema is machine readable, and is designed so dependencies can be easily matched to vulnerabilities using automation. The OSV Schema remains the only widely adopted schema that treats open source as a first class citizen. Since becoming a part of OpenSSF, the OSV Schema has seen adoption from services like GitHub, ecosystems such as Rust and Python, and Linux distributions such as Rocky Linux.

Thanks to such wide community adoption of the OSV Schema, OSV.dev is able to provide a distributed vulnerability database and service that pulls from language specific authoritative sources. In total, the OSV.dev database now includes 43,302 vulnerabilities from 16 ecosystems as of March 2023. Users can check OSV for a comprehensive view of all known vulnerabilities in open source.

Every vulnerability in OSV.dev contains package manager versions and git commit hashes, so open source users can easily determine if their packages are impacted because of the familiar style of versioning. Maintainers are also familiar with OSV’s community driven and distributed collaboration on the development of OSV’s database, tools, and schema.

Matching

The next step in managing vulnerabilities is to determine project dependencies and their associated vulnerabilities. Last December we released OSV-Scanner, a free, open source tool which scans software projects’ lockfiles, SBOMs, or git repositories to identify vulnerabilities found in the OSV.dev database. When a project is scanned, the user gets a list of all known vulnerabilities in the project.

In the two months since launch, OSV-Scanner has seen positive reception from the community, including over 4,600 stars and 130 PRs from 29 contributors. Thank you to the community, which has been incredibly helpful in identifying bugs, supporting new lockfile formats, and helping us prioritize new features for the tool.

Remediation

Once a vulnerability has been identified, it needs to be remediated. Removing a vulnerability through upgrading the package is often not as simple as it seems. Sometimes an upgrade will break your project or cause another dependency to not function correctly. These complex dependency graph constraints can be difficult to resolve. We’re currently working on building features in OSV-Scanner to improve this process by suggesting minimal upgrade paths.

Sometimes, it isn’t even necessary to upgrade a package. A vulnerable component may be present in a project, but that doesn’t mean it is exploitable–and VEX statements provide this information to help in prioritization of vulnerability remediation. For example, it may not be necessary to update a vulnerable component if it is never called. In cases like this, a VEX (Vulnerability Exploitability eXchange) statement can provide this justification.

Manually generating VEX statements is time intensive and complex, requiring deep expertise in the project’s codebase and libraries included in its dependency tree. These costs are barriers to VEX adoption at scale, so we’re working on the ability to auto-generate high quality VEX statements based on static analysis and manual ignore files. The format for this will likely be one or more of the current emerging VEX standards.

Compatibility

Not only are there multiple emerging VEX standards (such as OpenVEX, CycloneDX, and CSAF), there are also multiple advisory formats (CVE, CSAF) and SBOM formats (CycloneDX, SPDX). Compatibility is a concern for project maintainers and open source users throughout the process of identifying and fixing project vulnerabilities. A developer may be obligated to use another standard and wonder if OSV can be used alongside it.

Fortunately, the answer is generally yes! OSV provides a focused, first-class experience for describing open source vulnerabilities, while providing an easy bridge to other standards.

CVE 5.0

The OSV team has directly worked with the CVE Quality Working Group on a key new feature of the latest CVE 5.0 standard: a new versioning schema that closely resembles OSV’s own versioning schema. This will enable easy conversion from OSV to CVE 5.0, and vice versa. It also enables OSV to contribute high quality metadata directly back to CVE, and drive better machine readability and data quality across the open source ecosystem.

Other emerging standards

Not all standards will convert as effortlessly as CVE to OSV. Emerging standards like CSAF are comparatively complicated because they support broader use cases. These standards often need to encode affected proprietary software, and CSAF includes rich mechanisms to express complicated nested product trees that are unnecessary for open source. As a result, the spec is roughly six times the size of OSV and difficult to use directly for open source.

OSV Schema’s strong adoption shows that the open source community prefers a lightweight standard, tailored for open source. However, the OSV Schema maintains compatibility with CSAF for identification of packages through the Package URL and vers standards. CSAF records that use these mechanisms can be directly converted to OSV, and all OSV entries can be converted to CSAF.

SBOM and VEX standards

Similarly, all emerging SBOM and VEX standards maintain compatibility with OSV through the Package URL specification. OSV-Scanner today also already provides scanning support for the SPDX and CycloneDX SBOM standards.

OSV in 2023

OSV already provides straightforward compatibility with established standards such as CVE, SPDX, and CycloneDX. While it’s not clear yet which other emerging SBOM and VEX formats will become the standard, OSV has a clear path to supporting all of them. Open source developers and ecosystems will likely find OSV to be convenient for recording and consuming vulnerability information given OSV’s focused, minimal design.

OSV is not just built for open source, it is an open source project. We desire to build tools that will easily fit into your workflow and will help you identify and fix vulnerabilities in your projects. Your input, through contributions, questions, and feedback, is very valuable to us as we work towards that goal. Questions can be asked by opening an issue and all of our projects (OSV.dev, OSV-Scanner, OSV-Schema) welcome contributors.

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Want to keep up with the latest OSV developments? We’ve just launched a project blog! Check out our first major post, all about how VEX could work at scale.