VEX Hub is a centralized repository that collects and manages Vulnerability Exploitability eXchange (VEX) documents from various open-source software projects. It serves as a comprehensive resource for vulnerability information, helping users and security tools to efficiently access and utilize VEX data across multiple projects and ecosystems.

VEX Hub automatically retrieves VEX documents from source repositories of registered projects. By identifying the source repository from the registered Package URL (PURL), VEX Hub copies and organizes the VEX documents, making them easily accessible to the wider community.

Quick Start: Adding VEX Documents to VEX Hub

1. Create your VEX file
   1. VEX Hub supports OpenVEX or CSAF formats.
   2. Store your VEX files in your source code repository under the .vex/ directory at the root of your repository. More info here.
   3. For additional guidance on VEX Document Creation for VEX Hub, See here.
2. Register your package with VEX Hub
   1. Make a Pull Request that adds the PURL of your package to the crawled packages file.

That's it! VEX Hub will automatically retrieve and process your VEX documents.

VEX Crawling

VEX Hub Crawler periodically crawls VEX documents of registered packages and maintains them in VEX Hub. Registered packages are defined as a list of PURLs in [a file](purl-list] that can be updated by anyone through Pull Requests.

For detailed information on PURL registration, supported ecosystems, and specific requirements, please refer to VEX Hub Crawler.

Identifying Source Repositories

The packages file specifies only PURL of the package to be crawled, and VEX Hub Crawler automatically identifies the source code repository where the VEX file is located. The method for identifying source repositories varies by ecosystem. For detailed information on how source repositories are identified and crawled for different package types, please refer to the vex-crawler documentation.

Discovery of VEX Documents

After identifying the source code repository, VEX Hub automatically discovers VEX documents in it. The discovery process involves the following key points:

• VEX documents are searched for in the .vex/ directory at the root of the repository.
• Supported VEX formats are OpenVEX and CSAF.
• File names matching specific patterns (e.g., *.vex.json, *.csaf.json) are considered.
• PURLs must be used for products and subcomponents in the VEX documents.
• VEX documents not matching the registered PURL are ignored.

For detailed information on the discovery process, supported ecosystems, and specific requirements, please refer to the vex-crawler documentation.

Directory Structure

VEX Hub is structured based on the Package URL (PURL), excluding version, qualifiers and subpath. The structure adheres to the following rules:

1. The directory hierarchy is derived from the PURL's scheme, type, namespace (if present), and name components. In case of oci, the repository_url qualifier is used instead.
2. Version and qualifiers are omitted from the directory structure. These elements must be specified within the products field of the VEX documents.
3. URL encoding is applied to special characters in the PURL components.

Directory structure formation examples:

• pkg:npm/express → /npm/express/
• pkg:golang/github.com/gorilla/mux → /golang/github.com/gorilla/mux/
• pkg:maven/org.apache.xmlgraphics/batik-anim → /maven/org.apache.xmlgraphics/batik-anim/
• pkg:oci/trivy?repository_url=ghcr.io/aquasecurity/trivy → /oci/ghcr.io/aquasecurity/trivy/

Example with special character encoding:

• pkg:npm/@angular/core → /npm/%40angular/core/

Distribution

VEX Hub conforms to the VEX Repository Specification. The vex_repository.json and index.json files can be used to programmatically access VEX documents in VEX Hub.

Multiple VEX Documents per PURL

VEX Hub has the capability to store multiple VEX documents for a single PURL, as it copies all matching VEX documents from the source repository. However, the VEX Repository Specification allows only one VEX document per PURL. To comply with this specification, VEX Hub implements the following distribution strategy:

• When multiple VEX files exist for a single PURL, VEX Hub selects the first file in lexicographic order.
• Write the selected file to index.json for distribution.

VEX Document Creation for VEX Hub

To prevent confusion and ensure consistency, splitting VEX statements for the same PURL into multiple files is not recommended, as VEX Hub distributes only one VEX file per PURL.

The recommended approaches are:

1. Consolidate VEX statements for all products managed by the source repository into a single file.
2. Split VEX documents by PURL.

Example scenario: Consider a source repository https://github.com/org/repo that maintains two products, a Go module and an OCi image.

The first approach is to create a single VEX file, vex.json, containing VEX statements for both products.

• openvex.json: For both products, with PURLs pkg:golang/github.com/org/repo, pkg:oci/repo?repository_url=docker.io/org/repo and pkg:oci/repo?repository_url=ghcr.io/org/repo

The second approach is to create separate VEX files for each product.

• golang.vex: For the Go module, with PURL pkg:golang/github.com/org/repo
• oci.vex: For the OCI image, with PURLs, pkg:oci/repo?repository_url=docker.io/org/repo and pkg:oci/repo?repository_url=ghcr.io/org/repo

The following structure is not recommended:

• v1.vex: For the Go module, with PURL pkg:golang/github.com/org/[email protected]
• v2.vex: For the Go module, with PURL pkg:golang/github.com/org/[email protected]

In this example, v1.vex is selected for distribution, and v2.vex is ignored. They should be combined into a single VEX file, golang.vex, with multiple versions and qualifiers.

VEX HUB Trust Model

Since VEX Hub (and VEX in general) potentially augments security scanning results, you should be right to scrutinize the correctness of VEX documents that you consume. Unlike other Vulnerability Exchange feeds, or VEX-ready security advisory feeds, VEX Hub is not the data source of VEX statements. VEX Hub only aggregates existing VEX documents and organizes them into a central convenient repository.

In order to appear in VEX Hub, VEX documents needs to be committed into the source code repository of the main package first. This approach builds on the fact that as a user, you must already trust the packages that you use, and therefore maintainers, governance, and processes they employ. Each project has its own governance system and its own processes for committing into the source code repository. Those systems and processes that keep the package code trust-worthy in your eyes, are the same systems and processes that keep the VEX documents trust-worthy for you. You should not trust VEX Hub any more than you trust the packages that you choose to use.

VEX Hub does not have any responsibility or knowledge about the content of VEX documents it holds or the packages they describe. The VEX Hub maintainers do not review or vet the content of VEX documents, and the responsibility for the accuracy and correctness of the information lies with the originating package maintainers. We recommend that users manually triage suppressed vulnerabilities similarly to how they would triage any other vulnerability.

Troubleshooting

If VEX documents in the source repository of a registered PURL are not being updated properly in VEX Hub, please check the following:

1. Ensure that the VEX documents are placed in the correct location (.vex/ directory at the root of the repository).
2. Verify that the VEX documents use one of the supported file naming conventions.
3. Confirm that the PURL in the VEX document matches the registered PURL in VEX Hub.
4. Review the vexhub-crawler documentation to ensure all specifications for crawling are met.

If issues persist after confirming these points, please open an issue in the VEX Hub repository for further assistance.

Contributing

Contributions to improve VEX Hub are welcome! Please note that the packages list, and associated code is maintained in the VEX Hub Crawler repository. Pull Requests directly adding VEX documents to this repo are discouraged. This project and everyone participating in it is governed by the Aqua Security Code of Conduct.