Shared Responsibility Matrix (SRM) for CMMC 2.0: A Complete Guide for Defense Contractors

Why SRM is Critical for CMMC 2.0 Compliance 

As cybersecurity threats continue to grow, meeting CMMC 2.0 (Cybersecurity Maturity Model Certification) requirements has become a non-negotiable requirement for Department of Defense (DoD) contractors handling Controlled Unclassified Information (CUI). As the DoD tightens cybersecurity compliance, organizations must implement stringent security controls outlined in NIST SP 800-171 and DFARS 252.204-7012 to protect sensitive defense data. 

However, many small and mid-sized defense contractors don’t have the in-house expertise to manage every cybersecurity requirement on their own. To meet compliance and security demands, these organizations often outsource critical IT security functions to: 

• Cloud Service Providers (CSPs) – Hosting, encryption, and data protection solutions. 
• Managed Security Service Providers (MSSPs) – Threat detection, SOC monitoring, and incident response. 
• Security Operations Centers as a Service (SOCaaS) – 24/7 security monitoring and vulnerability management. 

While outsourcing can enhance security and streamline compliance, it also introduces a major challenge—who is responsible for meeting specific CMMC security controls? This is where the Shared Responsibility Matrix (SRM) becomes essential. 

What is an SRM & Why is it Critical for Compliance? 

A Shared Responsibility Matrix is a structured document that clearly defines security responsibilities between a contractor and its service providers. Without an SRM, CMMC assessors may find compliance gaps, leading to audit failures or delays in certification. By using an SRM, defense contractors can: 

	Ensure accountability for CMMC 2.0 security requirements.
	Avoid compliance risks associated with outsourced security services.
	Streamline CMMC assessments by demonstrating clear ownership of cybersecurity controls.

In this guide, we’ll cover what an SRM is, how to obtain one, its key components, and common pitfalls to avoid. Whether you’re preparing for a CMMC Level 2 or Level 3 assessment, understanding SRM will help you navigate compliance confidently and avoid regulatory pitfalls. 

What is a Shared Responsibility Matrix (SRM)? 

As CMMC 2.0 compliance becomes a top priority for DoD contractors, ensuring clear security responsibility allocation is critical. This is where the SRM comes into play. 

Defining the SRM 

SRM is a structured document that outlines which security responsibilities are handled by a contractor and which are managed by an external service provider. This includes CSPs, MSSPs, or SOC-as-a-Service providers. 

By defining ownership of security controls, the SRM helps contractors: 

	Avoid compliance gaps when outsourcing cybersecurity services.
	Demonstrate CMMC 2.0 compliance during assessments.
	Maintain proper documentation for assessors and auditors.

SRM vs. CRM: What’s the Difference? 

While both an SRM and a Customer Responsibility Matrix (CRM) define security responsibilities, they serve different purposes: 

If an organization manages security controls entirely in-house, a CRM is sufficient. However, if any security controls are outsourced to third parties, an SRM is required to document shared responsibilities. 

Example of an SRM in Action 

An SRM ensures that both the contractor and service provider know their exact roles for each CMMC 2.0 control. Below is an example of how security responsibilities might be allocated: 

How SRM Fits into CMMC 2.0 Compliance 

With CMMC 2.0, the DoD has reinforced strict cybersecurity requirements for contractors handling Controlled Unclassified Information (CUI). A key aspect of meeting CMMC compliance is ensuring that security responsibilities are properly assigned—especially when third-party service providers are involved. This is where the SRM becomes essential. 

CMMC 2.0’s Three Levels & SRM Requirements 

CMMC 2.0 consists of three distinct levels, each with varying security requirements: 

• Level 1 (Foundational) – Applies to contractors handling Federal Contract Information (FCI). Security is self-assessed and does not require an SRM. 

• Level 2 (Advanced) – Applies to contractors handling CUI. Requires third-party assessments and mandates compliance with NIST SP 800-171—where an SRM becomes essential for outsourced security controls. 

• Level 3 (Expert) – Applies to contractors working with highly sensitive CUI. Requires full NIST SP 800-171 & NIST SP 800-172 compliance, DoD-led assessments, and strict enforcement of shared security responsibilities. 

Key Takeaway: If your organization handles CUI (Level 2 or Level 3), an SRM is critical for proving cybersecurity responsibilities are properly allocated between you and your CSPs, MSSPs, or other vendors. 

Regulatory Tie-In: DFARS & NIST SP 800-171 

The Defense Federal Acquisition Regulation Supplement (DFARS) 252.204-7012 mandates that all contractors handling CUI implement NIST SP 800-171 security controls. Since many of these controls may be managed by an external provider, an SRM ensures proper compliance by documenting who is responsible for each requirement. 

An SRM helps demonstrate compliance with key NIST SP 800-171 controls, such as: 

	Access Control (AC) – Defining who manages identity & access management (IAM).
	Security Incident Response (IR) – Clarifying roles in threat detection & mitigation.
	Encryption (SC) – Establishing whether data encryption is managed by the CSP or internally.

Without an SRM, assessors may find compliance gaps, resulting in delays, audit failures, or contract risks. 

SRM’s Role in a CMMC 2.0 Assessment 

During a CMMC 2.0 third-party assessment, assessors will closely examine your SRM to verify: 

• Security responsibilities are explicitly assigned between the contractor and provider. 

• All NIST SP 800-171 requirements are covered, with no unassigned gaps. 
  Supporting documentation exists (e.g., security logs, policies, and contracts). 

A well-prepared SRM simplifies the CMMC assessment process, reducing the risk of compliance failures and ensuring CUI is adequately protected—even when outsourced security services are involved. 

Key Components of an SRM 

A Shared Responsibility Matrix is only effective if it is well-structured and clearly defines security responsibilities between a DoD contractor and its service providers. An SRM ensures that every cybersecurity control required under CMMC 2.0 is properly assigned, reducing compliance gaps and streamlining third-party assessments. 

Below are the key components of an SRM and how they help defense contractors achieve CMMC 2.0 compliance.

CMMC Control Reference

Each SRM entry must include the specific CMMC 2.0 control being addressed, which is typically mapped to NIST SP 800-171. This ensures assessors can quickly identify compliance alignment. 

Example: 
Control: AC.L2-3.1.1 (Limit access to authorized users and processes)

Control Description

This section explains what the security requirement entails and why it is important. It provides context for both the contractor and service provider. 

Example: 
Description: Ensure that only authorized personnel have access to CUI, and unauthorized users are restricted from system access.

Service Provider Responsibilities

Clearly defines the security tasks handled by the external provider, such as a MSSP, CSP, or Security Operations Center. 

Example: 
For AC.L2-3.1.1: 

	Enforce Identity and Access Management (IAM) policies.
	Manage role-based access control (RBAC) configurations.
	Maintain an audit log of all access requests.

Contractor Responsibilities

Outlines what the defense contractor must manage internally, ensuring security and compliance gaps are avoided. 

Example: 
For AC.L2-3.1.1: 

	Define authorized users and assign appropriate access roles.
	Conduct internal security awareness training on access control.
	Review IAM logs and monitor for unauthorized access attempts.

Shared Responsibilities

Some security controls require collaboration between the contractor and service provider. The SRM should specify which tasks require joint efforts to avoid miscommunication. 

Example: 
For AC.L2-3.1.1: 

	The service provider manages technical enforcement of IAM policies.
	The contractor ensures that only authorized personnel are approved for access.

Evidence & Documentation Requirements

CMMC 2.0 assessors require proof that all security responsibilities are being met. This section specifies the audit logs, policies, reports, and documentation needed to demonstrate compliance. 

Example: 
For AC.L2-3.1.1: 

	IAM logs showing access control enforcement.
	Role-based access policies and user access reviews.
	Incident response records for unauthorized access attempts.

SRM Example in Action 

Why a Well-Defined SRM Matters 

A well-structured SRM eliminates confusion, ensures that every CMMC 2.0 control is accounted for, and helps DoD contractors pass compliance audits without delays or failures. 

In the next section, we’ll explore how contractors can obtain an SRM and what to expect during the process. 

How to Obtain an SRM: What a Contractor Needs & What to Expect 

SRM is a critical document for CMMC 2.0 compliance, especially for Level 2 and Level 3 contractors handling CUI. Since many contractors outsource security services to Cloud Service Providers, MSSPs, or MSPs, obtaining a well-defined SRM is essential to demonstrate compliance during a CMMC assessment. 

Here’s how to obtain an SRM from your security provider, what to expect, and what assessors will look for. 

Requesting an SRM from Your Security Provider 

Most defense contractors must request an SRM from their CSP, MSSP, or MSP that is responsible for managing cybersecurity functions such as: 

• Cloud Security & Compliance (e.g., Microsoft GCC, AWS GovCloud) 
• Security Information & Event Management (SIEM) & SOC Monitoring 
• Access Control & Identity Management 
• Incident Detection & Response 

A well-structured SRM ensures clear role definitions between your organization and the provider, preventing compliance gaps that could jeopardize your CMMC certification. 

Critical Questions to Ask a Provider Before Obtaining an SRM 

Before accepting an SRM, contractors should ask the following questions to ensure it meets CMMC 2.0 and NIST SP 800-171 requirements: 

1.  Does the provider have an SRM aligned with CMMC 2.0 and NIST SP 800-171? 
   • Ensure the SRM is specifically mapped to the 110 security requirements in NIST SP 800-171. 
     
   
   
2. Does the SRM clearly define responsibility and ownership for each control? 
   • Verify that it explicitly states who (contractor vs. provider) is responsible for each security control. 
   
   
3. What security controls are fully managed vs. partially managed? 
   • Some security tasks may be shared, requiring clear documentation of joint responsibilities. 
   
   
4. Can the provider supply evidence (audit logs, security reports) during an assessment? 
   • CMMC assessors will require proof of security control implementation, so confirm that the provider can supply necessary audit logs, security policies, and compliance reports.

What to Expect in an SRM Document 

A comprehensive SRM should include: 

	CMMC/NIST 800-171 control mapping – Aligning each security requirement with responsibility ownership.
	Clear definitions of contractor vs. provider tasks – Ensuring no gaps exist.
	Detailed evidence requirements – Specifying audit logs, policies, incident response reports, and compliance documentation.

What CMMC Assessors Look for in an SRM 

During a CMMC 2.0 assessment, assessors will review your SRM to verify: 

• All CMMC 2.0 security requirements are assigned with no unaccounted controls. 
• Roles are clearly defined, avoiding ambiguity in cybersecurity responsibilities. 
• Documentation and logs exist to support compliance claims. 

Failure to present a well-structured SRM could lead to compliance issues, delays in certification, or even contract loss with the DoD. 

Obtaining a SRM is not just a compliance requirement—it’s a strategic move to protect CUI, avoid audit failures, and ensure a smooth CMMC certification process. By proactively working with security providers and ensuring your SRM aligns with NIST SP 800-171, your organization can confidently navigate CMMC 2.0 compliance. 

Next Up: Learn how to develop your own SRM when a provider does not supply one! 

How to Develop an SRM from Scratch 

If your CSP, MSSP, or MSP does not offer an SRM, you may need to develop one internally. Creating a well-structured SRM ensures your organization can accurately document security responsibilities and meet CMMC 2.0 compliance requirements. 

Follow this step-by-step guide to develop an SRM from scratch. 

Step 1: Identify External Providers Handling CUI or Security-Sensitive Functions 

Start by listing all third-party service providers that manage CUI or other security-critical operations. This includes: 

	Cloud Service Providers (CSPs) (e.g., AWS GovCloud, Microsoft GCC High)
	Managed Security Service Providers (MSSPs) (e.g., SIEM, SOC, MDR)
	Third-Party IT Support Vendors (e.g., outsourced IT help desks)

Each provider must be evaluated for their security role in protecting CUI. 

Step 2: Map Each CMMC 2.0 Control to the Responsible Party 

Next, align each CMMC security control to either: 

• The contractor (your organization) 
• The service provider (CSP, MSSP, MSP, SOC) 
• A shared responsibility between both 

Example: 

Ensure all 110 NIST SP 800-171 controls required for CMMC Level 2 are accounted for in the SRM. 

Step 3: Use an SRM Template (Excel, Smartsheet, or Compliance Software) 

To streamline the process, use an SRM template that includes: 

	CMMC Control Mapping – Reference specific controls (e.g., AC.L2-3.1.1).
	Responsibility Assignment – Clearly define roles for each party.
	Documentation Requirements – List required policies, logs, and evidence for audits.

Pro Tip: Using a structured template in Excel, Smartsheet, or compliance platforms or eMASS can help ensure accuracy and consistency. 

Step 4: Align Responsibilities with Contract Terms & SLAs 

Your SRM should align with contractual obligations in: 

• Service Level Agreements (SLAs) – Defining security performance metrics. 
• Data Protection & Compliance Clauses – Outlining compliance responsibilities. 
• Incident Response Agreements – Clarifying who is responsible for security incidents. 

Example: If a CSP manages firewall configurations, ensure this responsibility is contractually documented in the SLA. 

Step 5: Get Sign-Off from Leadership & Compliance Teams 

Before finalizing your SRM, obtain approval from: 

	Compliance Officers – To verify alignment with CMMC 2.0 & NIST SP 800-171.
	IT & Security Leadership – To ensure technical accuracy.
	External Providers (if applicable) – To confirm shared responsibility agreements.

A signed-off SRM ensures organizational accountability and audit readiness. 

Bonus: Get a Free SRM Template 

To help contractors build their CMMC-compliant SRM, we’ve created a downloadable SRM template in Excel format. 

Download Our Free SRM Template Here

A well-developed SRM provides clear security ownership, reduces compliance risks, and helps defense contractors pass CMMC 2.0 assessments. Whether working with CSPs, MSSPs, or other vendors, having a custom-built SRM ensures no security control is left unaccounted for. 

Common Pitfalls in SRM & How to Avoid Them 

SRM is a crucial tool for CMMC 2.0 compliance, but simply having one is not enough. Many DoD contractors make critical mistakes when using an SRM, which can lead to compliance failures, audit issues, and security gaps. Below are the most common pitfalls and how to avoid them to ensure a smooth CMMC assessment process.

Not Obtaining an SRM Before an Assessment

Pitfall: Some contractors wait until a CMMC 2.0 audit is scheduled before requesting an SRM, leaving them unprepared to prove compliance. 

Fix: Request an SRM early from your CSP, MSSP, or IT vendor. Having this document ready ahead of time ensures assessors can easily verify security responsibilities.

Unclear Responsibility Definitions

Pitfall: If roles are not explicitly defined, it can lead to security gaps, where neither the contractor nor the service provider takes ownership of a critical control. 

Fix: Ensure each CMMC 2.0 security requirement in the SRM has clear task ownership. Use specific terms like: 

	“The CSP is responsible for firewall configurations.”
	“The contractor must approve access control policies.”

This prevents miscommunication and ensures full compliance.

Inaccurate or Outdated SRM

Pitfall: Many organizations create an SRM once and never update it, even when vendor services change. This can cause misalignment with actual security practices, leading to audit failures. 

Fix: Regularly review and update the SRM to reflect: 

	Changes in vendor agreements or service offerings.
	CMMC 2.0 updates that impact compliance requirements.
	New technologies or security tools implemented.

Pro Tip: Schedule a quarterly SRM review with your compliance and security teams to keep it up to date.

Lack of Supporting Evidence

Pitfall: During an audit, assessors require proof that security controls are being enforced. Without logs, reports, or documentation, compliance claims are invalid. 

Fix: Maintain audit logs, policies, and reports for each assigned responsibility. Ensure that your provider can supply: 

	IAM logs & access control reports for identity management.
	SIEM & SOC monitoring logs for incident response.
	Data encryption reports for secure CUI transmission.

This evidence-based approach ensures CMMC compliance verification.

Failure to Review Shared Responsibilities

Pitfall: Some contractors assume that outsourced security functions are entirely managed by their provider, leading to gaps in shared responsibilities. 

Fix: Clearly define joint security responsibilities in the SRM. For example: 

	Service provider manages encryption (technical enforcement).
	Contractor ensures data is classified correctly (policy enforcement).

Pro Tip: Schedule regular check-ins with providers to confirm both parties are fulfilling their compliance obligations. 

A well-managed SRM is the key to CMMC 2.0 compliance success. Avoiding these common pitfalls will ensure accurate role definitions, up-to-date security policies, and well-documented evidence, reducing the risk of audit failures. 

Conclusion & Next Steps: Ensure CMMC 2.0 Compliance with a Strong SRM 

A Shared Responsibility Matrix (SRM) is more than just a document—it’s a critical component of CMMC 2.0 compliance. By clearly defining security responsibilities between contractors and service providers, an SRM helps eliminate compliance gaps, reduce cybersecurity risks, and streamline assessments. 

For CMMC Level 2 and Level 3 contractors, having a well-documented and up-to-date SRM is essential. Without it, organizations may struggle to prove who is responsible for key security controls, potentially leading to audit failures or delays in certification. 

Key Takeaway: Contractors should obtain an SRM early from their CSPs, MSSPs, or IT vendors—or develop one internally well before a CMMC assessment. 

Get Expert Guidance & Free Resources 

Need help preparing for your CMMC 2.0 assessment? Our experts at MAD Security specialize in CMMC compliance and cybersecurity solutions for defense contractors. 

Contact us today for a consultation on building a CMMC-compliant SRM! 

Download Our Free SRM Template Here to get started on your CMMC compliance journey today! 

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