Ensure IAM Role can be assumed only by specific Principals

AWS remediation

Console

1. Open IAM role trust policy.
2. Remove broad principals such as wildcard principal.
3. Allow only explicit trusted principals.
4. Add conditions like sts:ExternalId when third-party access is required.

AWS CLI

aws iam update-assume-role-policy \
  --role-name <role-name> \
  --policy-document file://trust-policy.json

References

• https://docs.aws.amazon.com/IAM/latest/UserGuide/id_roles_update-role-trust-policy.html
• https://docs.aws.amazon.com/cli/latest/reference/iam/update-assume-role-policy.html

Multiple Remediation Paths

AWS

SERVICE-WIDE (RECOMMENDED when many resources are affected): Deploy centralized guardrails and remediation using AWS Config Conformance Packs and (if applicable) AWS Organizations SCPs.

aws configservice put-organization-conformance-pack --organization-conformance-pack-name <pack-name> --template-s3-uri s3://<bucket>/<template>.yaml

ASSET-LEVEL: Apply the resource-specific remediation steps above to only the affected assets.

PREVENTIVE: Add CI/CD policy checks (CloudFormation/Terraform validation) before deployment to prevent recurrence.

References for Service-Wide Patterns

• AWS Config Conformance Packs: https://docs.aws.amazon.com/config/latest/developerguide/conformance-packs.html
• AWS Organizations SCP examples: https://docs.aws.amazon.com/organizations/latest/userguide/orgs_manage_policies_scps_examples.html

Operational Rollout Workflow

Use this sequence to reduce risk and avoid repeated drift.

1. Contain at Service-Wide Scope First (Recommended)

• AWS: deploy/adjust organization conformance packs and policy guardrails.

aws configservice put-organization-conformance-pack --organization-conformance-pack-name <pack-name> --template-s3-uri s3://<bucket>/<template>.yaml

2. Remediate Existing Affected Assets

• Execute the control-specific Console/CLI steps documented above for each flagged resource.
• Prioritize internet-exposed and production assets first.

3. Validate and Prevent Recurrence

• Re-scan after each remediation batch.
• Track exceptions with owner and expiry date.
• Add preventive checks in IaC/CI pipelines.