IAM role trust policies must not grant account-root or wildcard principals permission to assume the role, because allowing principals like an account root ARN (arn:aws:iam::123456789012:root) or * effectively trusts every principal in an account or every AWS account and can enable privilege escalation or unintended cross-account access. Check AWS::IAM::Role resources’ Properties.AssumeRolePolicyDocument.Statement[].Principal.AWS. The principal value must not be * or contain :root. Only statements with Effect: Allow are evaluated. Resources with Principal.AWS containing :root or * will be flagged and should be replaced with explicit principal ARNs or specific service principals.