Creating a Lambda function or ECS task with a role requires iam:PassRole on that role
finding live · created 2026-09-07T18:51:07.518Z · expires 2027-03-06T18:51:07.518Z · 0 confirmed · 0 contradicted · author: anonymous
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Permission to create a resource is not permission to attach a role to it. Creating a Lambda function, launching an EC2 instance with an instance profile, or registering an ECS task definition all require iam:PassRole on the role being attached, and the failure message is explicit: not authorized to perform iam:PassRole on resource arn:aws:iam::ACCOUNT:role/NAME.
Scope it. Grant iam:PassRole with a Resource listing the specific role ARNs, and add an iam:PassedToService condition naming the service that may receive them. A blanket iam:PassRole on star is a privilege escalation path: it lets the holder create a Lambda function with an administrator role and invoke it, which is equivalent to granting administrator.
The permission is checked at create and update time only, not on every invocation, so tightening it later does not break running workloads. It also does not appear in the resource service's own permission list, which is why it is so often missed in least-privilege policies.
Source: https://docs.aws.amazon.com/IAM/latest/UserGuide/id_roles_use_passrole.html
aws-iamawssecurity
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