CA-2(3): Leveraging Results from External Organizations

CA-2(3) requires you to accept and use control assessment results performed by qualified external organizations, but only after you confirm the assessment covers your system’s scope and meets your predefined quality and independence criteria. Operationalize it by defining acceptance criteria, validating external reports against those criteria, and documenting how you reuse results in your assessment plan and risk decisions. ¹

Key takeaways:

• Define “acceptable external assessment” upfront (assessor qualifications, independence, scope, methods, recency).
• Verify and document fit-for-purpose before reusing results; don’t paste in SOC/ISO reports without mapping.
• Retain a clear “reuse decision record” that ties external findings to your control assessment plan and POA&M. ²

The ca-2(3): leveraging results from external organizations requirement exists to reduce redundant testing while keeping your assurance defensible. In practice, you’ll see it during ATO work, annual control assessments, continuous monitoring, and third-party risk efforts where you already have external evidence like SOC 2 reports, ISO 27001 certificates, penetration test reports, FedRAMP packages, or independent audits from other business units.

CA-2(3) does not mean “accept any external report.” It means you set conditions for reuse, then you reuse results only when those conditions are met. The operational challenge is consistency: different report types test different things, at different depths, under different scopes, and with different degrees of independence. Auditors will focus on whether you had a rational basis to rely on the external work and whether you can show traceability from external test steps to your control determination.

This page gives you requirement-level implementation guidance: who owns the decision, what your procedure should look like, what evidence to keep, and the common ways teams fail this control. ²

Regulatory text

Control enhancement CA-2(3): “Leverage the results of control assessments performed by [external organizations] on [organization-defined controls] when the assessment meets [organization-defined requirements].” ¹

What the operator must do:

1. Decide which external organizations’ assessments you will accept (and under what conditions).
2. Decide which controls you will allow to be covered by external results.
3. Define the “meets requirements” gate (quality, independence, scope fit, and any other conditions).
4. Reuse external results only after passing the gate, and document the decision and how it impacts your assessment conclusions. ²

Plain-English interpretation

CA-2(3) lets you reuse credible outside assessment work so you don’t re-test the same controls, but it requires discipline:

• You must predefine acceptance criteria for external assessments.
• You must confirm the external assessment actually tests what you need, for the correct system boundary, time period, and control intent.
• You must record how the external results change your control assessment plan, including what you no longer test yourself and what compensating checks you keep.

A good mental model: external results can replace or reduce your testing only when you can defend equivalence between what they tested and what you need to conclude for your system. ²

Who it applies to

Entities

• Federal information systems and programs implementing NIST SP 800-53 control assessment requirements. ²
• Contractors handling federal data (common in environments aligned to NIST 800-53 for ATO/FedRAMP-like expectations, or when customers contractually require 800-53 controls). ²

Operational contexts where CA-2(3) shows up

• Annual or recurring internal control assessments (CA-2) and continuous monitoring.
• ATO packages where you want to reuse prior assessments from another authorizing official, an independent assessor, or a shared service.
• Third-party relationships where you want to reuse SOC 2/ISO results to support your own control conclusions, without overstating what those reports cover. ²

What you actually need to do (step-by-step)

1) Assign ownership and decision rights

Create a simple RACI for external assessment reuse:

• Accountable: CISO/CCO/GRC lead (who signs off on reliance).
• Responsible: Control assessment lead (who runs the validation).
• Consulted: Control owners, legal/procurement, vendor/third-party risk (as relevant).
• Informed: System owner, internal audit.

This avoids the common failure mode where a procurement team accepts a report and GRC later treats it as control evidence without a technical review. ²

2) Define “acceptable external assessment” criteria (your gate)

Document acceptance criteria in a short standard (one page is fine). Include:

Assessor credibility

• Who performed the assessment (independent audit firm, accredited certifier, qualified internal audit function, government assessor).
• Minimum qualifications and independence expectations (you define these). ¹

Scope fit

• System/environment covered (must match your boundary or be clearly mappable).
• Services/locations in scope, and carve-outs.
• Time period and any major change since assessment.

Method rigor

• Evidence type (tests of design vs operating effectiveness, sampling, interview-only, automated scans).
• Clear mapping to control objectives you need to satisfy.

Risk acceptance rules

• When you still require supplemental testing (for example, high-risk controls, compensating controls, or where the report has exceptions you must resolve).

Write these as pass/fail checks so reviewers can apply them consistently. ¹

3) Create a control-to-report mapping method

Build a mapping worksheet that answers, control by control:

• Which CA-2 control objective are you trying to satisfy?
• Which external document section supports it?
• What is the coverage statement (full/partial/none)?
• What residual test steps will you perform internally?

Example mapping use cases (practical):

• A SOC 2 report may support certain operational controls, but you still may need system-specific configuration evidence.
• A penetration test can support testing for specific technical controls, but it rarely covers policy/process controls by itself.

Do not allow “SOC 2 exists” as the mapping. Require pinpoint references. ²

4) Validate the external assessment against your gate

Run a structured intake review:

1. Confirm document authenticity and version (final report, not a marketing summary).
2. Confirm the assessed entity matches your third party and the services you consume.
3. Review exceptions, qualified opinions, and “user entity controls” or “customer responsibilities” sections.
4. Decide whether the external work fully satisfies, partially satisfies, or does not satisfy each relevant control objective.

Result: a documented decision that external results are acceptable for reuse, plus defined supplemental steps. ²

5) Update your assessment plan and test program

CA-2(3) is not finished when you accept the report. You must reflect reuse in your program:

• Update the control assessment plan to indicate which controls will be assessed via external results.
• Update test procedures to avoid duplicate testing.
• Add targeted internal validation where the external report is weak, stale, or mis-scoped.

Auditors look for alignment between your “we rely on X” statement and your actual testing cadence and evidence. ²

6) Track gaps into POA&M / issues management

If the external assessment includes findings relevant to your environment (or gaps in coverage), treat them like any other assessment result:

• Log issues, owners, remediation approach, and due dates in your tracking system.
• Document risk acceptance where remediation is not required or is deferred.

This is where teams often drop the ball: they accept external results but never operationalize the exceptions. ²

7) Operationalize recurring intake (continuous monitoring)

Create a recurring trigger for re-validation:

• Material changes (provider acquisition, major platform change, new regions).
• Contract renewal / annual evidence refresh.
• Significant incidents affecting the third party.

Keep the gate the same; only the inputs change. ²

Required evidence and artifacts to retain

Keep evidence in an auditor-friendly package per external assessment:

1. External assessment artifact

• Full report (SOC/ISO/audit report/pentest report), including scope, period, and exceptions.

2. Acceptance criteria

• Your documented gate (criteria for external organization, controls in scope, and “meets requirements”). ¹

3. Mapping worksheet

• Control-to-report crosswalk with coverage determinations and citations to report sections.

4. Reuse decision record

• Sign-off (who approved reliance), rationale, residual risk notes, and required supplemental testing.

5. Assessment plan update

• Evidence your CA-2 assessment plan reflects reuse, including what you did not retest and why. ²

6. Issue tracking

• POA&M entries or risk acceptances tied to report exceptions and gaps.

If you use Daydream to manage third-party due diligence and control evidence, the “reuse decision record” becomes a repeatable workflow: intake, gate checks, mapping, approvals, and a retained audit trail that shows exactly why you relied on the external work and what you did to close coverage gaps.

Common exam/audit questions and hangups

Expect questions like:

• “Show me your criteria for accepting external assessments. Who approved it?” ¹
• “How did you confirm the report scope matches your system boundary and services consumed?”
• “Which controls did you mark as satisfied by external results, and where in the report is the evidence?”
• “What did you do about exceptions, subservice organizations, or customer responsibility controls?”
• “How do you handle stale reports or material changes since the assessment?”

Hangups auditors see repeatedly:

• Report is high-level and doesn’t support operating effectiveness for your specific control statements.
• “Bridge letters” or partial updates are treated as full coverage without analysis.
• Reliance is informal (email threads) rather than a controlled decision with sign-off and mapping.

Frequent implementation mistakes (and how to avoid them)

Mistake	Why it fails CA-2(3)	Fix
Accepting a SOC 2/ISO certificate as blanket compliance	Scope and control objectives rarely align 1:1	Require a control-by-control mapping and document partial coverage
No defined acceptance criteria	You can’t prove the assessment “meets requirements”	Publish a short standard: assessor credibility, scope fit, rigor, recency triggers 1
Ignoring exceptions/user-entity controls	You inherit the gaps	Convert exceptions into issues, supplemental tests, or risk acceptances
Reusing results without updating your assessment plan	Your program contradicts your reliance claim	Update test procedures and document where external evidence replaces testing 2
Treating third-party evidence as static	External environments change	Add change triggers and periodic re-validation tied to procurement and security monitoring

Risk implications (what can go wrong)

CA-2(3) is a “defensibility” control. Failures typically show up as:

• Overstated assurance (you claim controls are effective based on evidence that doesn’t test your control statement).
• Missed inherited-control gaps (subservice providers, carve-outs, customer responsibilities).
• Duplicative testing (wasted effort) because teams don’t trust external work or don’t document reliance.

The risk is operational and regulatory: if an incident occurs, your post-incident narrative will be judged against what you said you relied on and why that reliance was reasonable. ²

Practical execution plan (30/60/90-day)

You asked for speed. Use a phased plan without pretending every environment fits a fixed calendar.

First 30 days: Stand up the gate and intake

• Name an accountable owner and approvers for reuse decisions.
• Publish acceptance criteria for external assessment reuse (one-page standard).
• Create the mapping worksheet template and reuse decision record template.
• Pilot on one high-impact external report you already have (SOC 2, ISO, FedRAMP package, or pen test). ¹

By 60 days: Convert to repeatable operations

• Train assessors/control owners on how to map controls to external evidence.
• Update your control assessment plan to include an “external results” testing path.
• Implement issue intake from external reports into POA&M/risk register.
• Add procurement/TPRM checkpoints so new third parties trigger the reuse gate review. ²

By 90 days: Scale and audit-proof

• Build a library of “pre-mapped” common external report types to your control catalog, with clear rules for what can never be fully inherited.
• Add change triggers (material change, incident, renewal) and assign monitoring owners.
• Run an internal QA review: pick several controls marked as “externally assessed” and verify traceability from control statement to report section to approval record.
• If you use Daydream, standardize evidence collection and approvals so every reuse decision produces the same audit-ready artifact set.

Frequently Asked Questions

What counts as an “external organization” for CA-2(3)?

Any organization outside your system’s direct control that performed a control assessment you want to rely on, such as an independent auditor, a certification body, or a government/third-party assessor. Your acceptance criteria should define which external sources you accept. ¹

Can I rely on a SOC 2 report to satisfy CA-2(3)?

You can, if the SOC 2 scope and test procedures match your control objectives and the report meets your acceptance criteria. Keep a mapping that cites specific SOC 2 sections and addresses exceptions and customer responsibility controls. ²

Do I still need to perform internal testing if I accept an external assessment?

Often yes, for boundary-specific configurations, controls not covered by the report, or where the report has carve-outs or exceptions. CA-2(3) permits reuse when requirements are met; it does not require you to stop all internal testing. ¹

How do I handle external assessment findings that don’t apply to my deployment?

Document the rationale in your reuse decision record and show the scoping logic (which service/features you consume and which you don’t). Auditors will accept “not applicable” only when it is supported by clear boundary and architecture facts. ²

What if the external report is older or the third party changed their environment?

Treat that as a gate failure or partial coverage until you have an updated report or supplemental testing that addresses the change. Define the change triggers in your acceptance criteria so teams don’t debate this case-by-case. ²

What’s the minimum documentation to prove compliance with CA-2(3)?

Keep the external report, your acceptance criteria, a control mapping, and an approval record that states which controls are covered and what you did about gaps. If any exceptions exist, retain the linked POA&M or risk acceptance. ²

Footnotes

1. NIST SP 800-53 Rev. 5 OSCAL JSON

2. NIST SP 800-53 Rev. 5