Open Source as a Third-Party Risk

Open-source software components are a form of third-party risk that most TPRM programmes do not address , because they are not vendor relationships in the traditional sense. There is no contract, no questionnaire, no vendor contact, and no commercial relationship. The open-source library is code integrated into the enterprise's own applications, created and maintained by individuals or communities outside the enterprise's control, and subject to the same supply chain attack vectors as commercial software without the contractual security obligations that commercial vendor relationships impose. Treating open-source components as internal code rather than third-party dependencies leaves a significant portion of the enterprise's actual supply chain unmanaged.

The dependency inventory gap is the foundation of open-source risk management. An enterprise that does not know which open-source libraries its applications depend on cannot assess the security risk those libraries represent, cannot monitor for vulnerability disclosures in those libraries, and cannot remediate vulnerabilities when they are discovered without first determining which applications are affected. Software Composition Analysis is the tool category that provides open-source dependency inventory , scanning application codebases to identify all third-party libraries, their versions, and known vulnerabilities.

Why this matters

Open-source as third-party risk matters because the most significant supply chain attacks of the past decade have targeted open-source components , Log4Shell, XZ Utils backdoor, event-stream, and similar attacks all exploited the trust that software built on open-source components extends to those components. The enterprise that has assessed all its commercial vendors thoroughly while leaving its open-source dependency chain unmanaged has addressed the visible supply chain while leaving the invisible one unprotected.

• Open-source libraries not in TPRM scope , treated as internal code
• No open-source dependency inventory
• No vulnerability monitoring for open-source dependencies
• No remediation process for open-source vulnerabilities
• Maintainer health not assessed , single-maintainer abandoned libraries

What good looks like

Mature open-source risk programmes implement SCA tooling as a standard part of the software development and deployment pipeline, maintain a current SBOM for all production applications, monitor for vulnerability disclosures in dependency libraries, and define remediation SLAs for critical and high-severity open-source vulnerabilities.

• SCA tooling in CI/CD pipeline , automated dependency scanning
• SBOM maintained for all production applications
• Vulnerability monitoring for all open-source dependencies
• Remediation SLA for critical open-source vulnerabilities
• Maintainer health assessment for high-risk dependencies

Tooling

SCA , Snyk, OWASP Dependency-Check, GitHub Dependabot, Sonatype Nexus for open-source vulnerability monitoring

Software Composition Analysis tools provide automated scanning of codebases for open-source library inventory and vulnerability status. Snyk, Dependabot, and OWASP Dependency-Check are widely used options with different integration models. For TPRM programmes, SCA tooling extends the programme's scope to the open-source supply chain that commercial vendor assessment does not reach.

Governance challenges

The governance challenge with open-source as TPRM is the programme scope question. Traditional TPRM programmes are organised around vendor relationships. Open-source risk is typically owned by application security or development teams. The governance resolution is a formal connection between TPRM and application security programmes , ensuring that open-source supply chain risk is tracked in a programme that has visibility into production applications, not siloed in a security tool that no one is systematically acting on.

• Extend TPRM scope or connect to AppSec programme for open-source risk
• Implement SCA tooling in development pipeline
• Maintain SBOM for production applications
• Define remediation SLA for critical open-source vulnerabilities
• Include open-source supply chain in TPRM risk register

If you are a small team

Enable GitHub Dependabot or equivalent automated vulnerability scanning for your production code repositories. Within 48 hours you will have a dependency inventory and a list of known vulnerabilities in your open-source libraries. Review the critical and high-severity findings. That list , generated automatically from your existing code , is the open-source supply chain risk picture that your TPRM programme has not been seeing.

• Enable Dependabot or SCA tool for production repositories
• Review critical and high-severity dependency vulnerabilities
• Create open-source vulnerability remediation SLA
• Connect SCA programme output to TPRM risk register

What to require

Ask directly:

"Do you maintain a software bill of materials for your product , and are your open-source dependencies monitored for vulnerability disclosures with defined remediation SLAs for critical and high-severity findings?"

Expect as evidence

• Software Bill of Materials for product
• SCA tooling and vulnerability monitoring confirmation
• Remediation SLA for open-source vulnerabilities
• Critical open-source dependency health assessment

A vendor who confirms application security should be asked about their SBOM and open-source vulnerability management. Commercial vendor assessment covers the vendor's own security programme. The SBOM and SCA programme covers the open-source supply chain running inside their product.

How to evidence it

• SCA tooling implementation records
• SBOM maintenance
• Open-source vulnerability remediation SLA
• TPRM scope extension to include open-source risk

Key Takeaway

847 commercial vendors assessed. 847 open-source libraries unmanaged. Critical vulnerability: 14 applications affected, no inventory, no process. The TPRM programme covered the commercial vendor risk thoroughly. The open-source supply chain running underneath the commercial products and the enterprise's own applications was outside the programme's scope. Log4Shell, XZ Utils, event-stream , the most significant supply chain attacks of recent years targeted open-source components. SCA tooling, SBOM maintenance, and vulnerability monitoring extend the TPRM programme's reach to the supply chain that commercial vendor assessment doesn't address.

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