- A
Add an allow statement for the vendor in the role’s trust policy to permit sts:AssumeRole from the vendor account (and include any required ExternalId condition).
AssumeRole is blocked unless the role trust policy allows the vendor principal. The role’s permissions policy alone cannot permit assumption.
- B
Attach the same allow policy to the vendor account’s existing IAM user so the user can call sts:AssumeRole directly into your role.
Why wrong: Even if the vendor user can call sts:AssumeRole, your role still must trust that principal. Without trust, the AssumeRole request is denied.
- C
Replace the AssumeRole call with GetCallerIdentity so the vendor can infer permissions without assuming the role.
Why wrong: GetCallerIdentity does not grant access to the internal resources. The vendor still needs a trusted identity and proper permissions.
- D
Enable MFA on the vendor’s IAM user and require MFA for your role using condition keys in the permissions policy.
Why wrong: MFA requirements affect the authorization flow but do not solve the root cause. The trust policy must first allow the vendor to assume the role.
Quick Answer
The answer is to add an allow statement for the vendor in the role’s trust policy to permit sts:AssumeRole from the vendor account, including any required ExternalId condition. This is correct because the "Not authorized to perform: sts:AssumeRole" error means the role’s trust policy—which defines who is allowed to assume the role—does not list the external AWS account as a trusted principal; the permissions policy attached to the role only controls what actions the role can perform once assumed, not who can assume it. On the SAA-C03 exam, this scenario tests your understanding of the critical distinction between a role’s trust policy (who can assume) and its permissions policy (what they can do), and it often appears as a trap where candidates mistakenly try to fix the permissions policy instead. A common memory tip is "Trust for who, Permissions for what"—the trust policy is the gatekeeper that must explicitly allow the external account’s ARN, and adding an ExternalId condition prevents the confused deputy problem.
SAA-C03 Design Secure Architectures Practice Question
This SAA-C03 practice question tests your understanding of design secure architectures. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. A key principle to apply: iAM role trust policies define who can assume the role.. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A security analyst needs to let an external vendor (AWS account 555566667777) read data from a set of internal resources in your AWS account. You created an IAM role called VendorReadRole with a policy that allows the required API calls. However, when the vendor tries to access, CloudTrail shows the call fails at AssumeRole with: "Not authorized to perform: sts:AssumeRole".
What is the most appropriate fix?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Add an allow statement for the vendor in the role’s trust policy to permit sts:AssumeRole from the vendor account (and include any required ExternalId condition).
The error 'Not authorized to perform: sts:AssumeRole' indicates that the role's trust policy does not grant the external AWS account (555566667777) permission to assume the role. The trust policy must include an Allow statement with the sts:AssumeRole action, specifying the external account as the principal, and optionally an ExternalId condition to prevent the confused deputy problem. This is the required configuration for cross-account IAM role access.
Key principle: IAM role trust policies define who can assume the role.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Add an allow statement for the vendor in the role’s trust policy to permit sts:AssumeRole from the vendor account (and include any required ExternalId condition).
Why this is correct
AssumeRole is blocked unless the role trust policy allows the vendor principal. The role’s permissions policy alone cannot permit assumption.
Related concept
IAM role trust policies define who can assume the role.
- ✗
Attach the same allow policy to the vendor account’s existing IAM user so the user can call sts:AssumeRole directly into your role.
Why it's wrong here
Even if the vendor user can call sts:AssumeRole, your role still must trust that principal. Without trust, the AssumeRole request is denied.
- ✗
Replace the AssumeRole call with GetCallerIdentity so the vendor can infer permissions without assuming the role.
Why it's wrong here
GetCallerIdentity does not grant access to the internal resources. The vendor still needs a trusted identity and proper permissions.
- ✗
Enable MFA on the vendor’s IAM user and require MFA for your role using condition keys in the permissions policy.
Why it's wrong here
MFA requirements affect the authorization flow but do not solve the root cause. The trust policy must first allow the vendor to assume the role.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse the role's permissions policy (which defines what the role can do after being assumed) with the trust policy (which defines who can assume the role), and mistakenly think attaching permissions to the external user or modifying the permissions policy will fix the AssumeRole authorization failure.
Detailed technical explanation
How to think about this question
When an external AWS account assumes a role, the trust policy acts as a resource-based policy on the role itself, granting the external principal permission to call sts:AssumeRole. The ExternalId condition is a best practice to prevent the confused deputy problem, where a malicious third party could trick the role into being assumed by an unintended account. Under the hood, the sts:AssumeRole API returns temporary security credentials (access key, secret key, session token) that are valid for a configurable duration (default 1 hour, max 12 hours).
KKey Concepts to Remember
- IAM role trust policies define who can assume the role.
- The `sts:AssumeRole` action must be allowed in the trust policy for cross-account access.
- An `ExternalId` condition enhances security against confused deputy attacks.
- A role's permissions policy defines what actions the assumed role can perform, not who can assume it.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
IAM role trust policies define who can assume the role.
Real-world example
How this comes up in practice
A company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
What to study next
Got this wrong? Here's your next step.
Review iAM role trust policies define who can assume the role., then practise related SAA-C03 questions on the same topic to reinforce the concept.
- →
Design Secure Architectures — study guide chapter
Learn the concepts, then practise the questions
- →
Design Secure Architectures practice questions
Targeted practice on this topic area only
- →
All SAA-C03 questions
1,040 questions across all exam domains
- →
SAA-C03 study guide
Full concept coverage aligned to exam objectives
- →
SAA-C03 practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Related SAA-C03 practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Design Secure Architectures practice questions
Practise SAA-C03 questions linked to Design Secure Architectures.
Design Resilient Architectures practice questions
Practise SAA-C03 questions linked to Design Resilient Architectures.
Design High-Performing Architectures practice questions
Practise SAA-C03 questions linked to Design High-Performing Architectures.
Design Cost-Optimized Architectures practice questions
Practise SAA-C03 questions linked to Design Cost-Optimized Architectures.
SAA-C03 VPC practice questions
Practise SAA-C03 questions linked to SAA-C03 VPC.
SAA-C03 S3 lifecycle policy questions
Practise SAA-C03 questions linked to SAA-C03 S3 lifecycle policy questions.
SAA-C03 RDS Multi-AZ questions
Practise SAA-C03 questions linked to SAA-C03 RDS Multi-AZ questions.
SAA-C03 IAM policy practice questions
Practise SAA-C03 questions linked to SAA-C03 IAM policy.
SAA-C03 Route 53 failover questions
Practise SAA-C03 questions linked to SAA-C03 Route 53 failover questions.
SAA-C03 CloudFront practice questions
Practise SAA-C03 questions linked to SAA-C03 CloudFront.
SAA-C03 NAT gateway questions
Practise SAA-C03 questions linked to SAA-C03 NAT gateway questions.
SAA-C03 VPC endpoint questions
Practise SAA-C03 questions linked to SAA-C03 VPC endpoint questions.
Practice this exam
Start a free SAA-C03 practice session
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
FAQ
Questions learners often ask
What does this SAA-C03 question test?
Design Secure Architectures — This question tests Design Secure Architectures — IAM role trust policies define who can assume the role..
What is the correct answer to this question?
The correct answer is: Add an allow statement for the vendor in the role’s trust policy to permit sts:AssumeRole from the vendor account (and include any required ExternalId condition). — The error 'Not authorized to perform: sts:AssumeRole' indicates that the role's trust policy does not grant the external AWS account (555566667777) permission to assume the role. The trust policy must include an Allow statement with the sts:AssumeRole action, specifying the external account as the principal, and optionally an ExternalId condition to prevent the confused deputy problem. This is the required configuration for cross-account IAM role access.
What should I do if I get this SAA-C03 question wrong?
Review iAM role trust policies define who can assume the role., then practise related SAA-C03 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
IAM role trust policies define who can assume the role.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Same concept, more angles
1 more ways this is tested on SAA-C03
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A security analyst needs to let an external vendor (AWS account 555566667777) read data from a set of internal resources in your AWS account. You created an IAM role called VendorReadRole with a policy that allows the required API calls. However, when the vendor tries to access, CloudTrail shows the call fails at AssumeRole with: "Not authorized to perform: sts:AssumeRole". What is the most appropriate fix?
medium- ✓ A.Add an allow statement for the vendor in the role’s trust policy to permit sts:AssumeRole from the vendor account (and include any required ExternalId condition).
- B.Attach the same allow policy to the vendor account’s existing IAM user so the user can call sts:AssumeRole directly into your role.
- C.Replace the AssumeRole call with GetCallerIdentity so the vendor can infer permissions without assuming the role.
- D.Enable MFA on the vendor’s IAM user and require MFA for your role using condition keys in the permissions policy.
Why A: The error 'Not authorized to perform: sts:AssumeRole' indicates that the role's trust policy does not grant the external AWS account (555566667777) permission to assume the role. The trust policy must include an Allow statement with the sts:AssumeRole action, specifying the external account as the principal, and optionally an ExternalId condition to prevent the confused deputy problem. Without this trust policy configuration, even if the permissions policy allows the required API calls, the vendor cannot assume the role.
Last reviewed: Jun 11, 2026
This SAA-C03 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the SAA-C03 exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.