The mandatory adoption of Software Bills of Materials (SBOMs) across numerous sectors has been a significant step forward for cybersecurity. We can now see the components that make up our software, but this newfound visibility has created a new problem: alert fatigue. Your scanner flags a critical CVE in a transitive dependency – a dependency of a dependency – and panic ensues. But is the sky really falling?
This is where the Vulnerability Exploitability eXchange (VEX) comes in. VEX is a game-changer for developers, AppSec engineers, and DevSecOps practitioners, allowing them to cut through the noise and focus on the vulnerabilities that truly matter. This guide will provide a practical walkthrough of how to use VEX to triage a critical dependency CVE and build an automated workflow to prioritize patching.
## The SBOM-Induced Headache: A Sea of Red
You’ve done your due diligence. You have an SBOM for your application, and you’re regularly scanning it for vulnerabilities. But then it happens: a critical CVE is discovered in a library that you’ve never even heard of. It’s a transitive dependency, buried deep in your dependency tree.
The immediate reaction is to scramble the jets and patch the vulnerability. But what if the vulnerable function is never actually called by your code? What if the vulnerability is only exploitable under certain conditions that don’t apply to your application? This is the problem that VEX was created to solve.
## VEX to the Rescue: A Declaration of Exploitability
VEX is a security advisory that provides information about the exploitability of a vulnerability in a specific context. It’s a way for a software supplier to say, “Yes, this component is vulnerable, but we don’t use the vulnerable part of it, so you’re not affected.”
A VEX advisory can be used to:
* **Confirm a vulnerability:** The supplier can confirm that a vulnerability is exploitable in their product.
* **Dispute a vulnerability:** The supplier can dispute the existence of a vulnerability.
* **Mark a vulnerability as “not exploitable”:** The supplier can declare that a vulnerability is not exploitable in their product.
* **Mark a vulnerability as “in triage”:** The supplier can indicate that they are still investigating the vulnerability.
By using VEX, you can significantly reduce the number of false positives in your vulnerability scans and focus your patching efforts on the vulnerabilities that pose a real risk to your organization.
## Tools of the Trade: Correlating SBOMs with VEX Data
There are a number of tools available that can help you to correlate your SBOMs with VEX data. Here are a few of the most popular:
* **Grype:** Grype is a popular open-source vulnerability scanner that can be used to scan container images and filesystems. It has built-in support for VEX, allowing you to filter out vulnerabilities that are not exploitable in your context.
* **Trivy:** Trivy is another popular open-source vulnerability scanner that supports VEX. It can be used to scan a variety of artifacts, including container images, filesystems, and Git repositories.
* **Dependency-Track:** Dependency-Track is an open-source platform that allows you to manage your SBOMs and track your vulnerabilities. It has built-in support for VEX, allowing you to automate the process of triaging vulnerabilities.
## Building an Automated Workflow: From Noise to Actionable Intelligence
The real power of VEX comes from its ability to be integrated into an automated workflow. Here’s a high-level overview of how to build such a workflow:
1. **Ingest SBOM:** The first step is to ingest your SBOM into a tool like Dependency-Track.
2. **Scan for CVEs:** Next, you’ll need to scan your SBOM for CVEs using a tool like Grype or Trivy.
3. **Enrich with VEX/EPSS Data:** Once you have a list of CVEs, you can enrich it with VEX and EPSS (Exploit Prediction Scoring System) data. This will help you to prioritize your patching efforts.
4. **Auto-Generate Tickets:** Finally, you can auto-generate tickets only for the vulnerabilities that are truly exploitable. This will allow your developers to focus on fixing the vulnerabilities that matter most.
## Conclusion
The combination of SBOMs and VEX is a powerful one. It allows you to move from a world of noisy, unactionable vulnerability alerts to a world of targeted, actionable intelligence. By embracing this new paradigm, you can significantly improve your security posture and reduce the risk of a breach. The days of chasing ghosts in your dependency tree are over. It’s time to put VEX to work.
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