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العربيةRewrite role trust, then assume
Can rewrite a role's trust policy and then assume it.
Grants escalation only in combination. All of these are needed together:
iam:UpdateAssumeRolePolicysts:AssumeRoleiam:UpdateAssumeRolePolicy can rewrite a role's trust policy and then assume it, but only when it is held together with sts:AssumeRole. Held together they reach administrator access.
Why it is dangerous
A principal can call iam:UpdateAssumeRolePolicy to rewrite the trust policy of the role so that it trusts the principal, then call sts:AssumeRole to take it over. This two-step move lets the principal commandeer any role in the account regardless of its original trust, if the target role is privileged, that is direct privilege escalation. (Both actions are required: rewriting trust is useless without the follow-up assume.)
In MITRE ATT&CK terms this maps to T1098.003, Account Manipulation: Additional Cloud Roles, under the privilege escalation tactic. AWS records it in CloudTrail as UpdateAssumeRolePolicy, AssumeRole. The call shows up in CloudTrail but blends into normal administration, so it needs a rule to stand out. It also gives an attacker a way to keep access after the first foothold is closed, so it is worth watching even when it looks like routine administration.
Detection
UpdateAssumeRolePolicyAssumeRolePrerequisites
Holds sts:AssumeRole as well, to use the role after rewriting its trust.
Tactic
Privilege Escalation
A control that would remove it: Remove iam:UpdateAssumeRolePolicy from the principal.
Whether to apply it depends on how the permission is used in your environment, so it is a business decision rather than an automatic fix. The same permission can be load-bearing in one account and pure risk in another.
Pathbreak confirms whether this path resolves in your account, ranks it against the others by how much it opens up, and uses your threat model and business context to show which paths are worth cutting.
Questions
What does iam:UpdateAssumeRolePolicy allow?
Can rewrite a role's trust policy and then assume it.
What else is needed for iam:UpdateAssumeRolePolicy to be dangerous?
It becomes an escalation only when held together with sts:AssumeRole. On its own it is not enough, which is what makes the combination easy to miss.
How is rewrite role trust, then assume detected?
Watch for UpdateAssumeRolePolicy, AssumeRole in CloudTrail. The call shows up in CloudTrail but blends into normal administration, so it needs a rule to stand out.
How do you break this path?
A control that would remove it is: Remove iam:UpdateAssumeRolePolicy from the principal. Whether to apply it depends on how the permission is used in your account, so it is a business decision rather than an automatic fix.
Which MITRE ATT&CK technique is this?
T1098.003, Account Manipulation: Additional Cloud Roles, under the privilege escalation tactic.
Related paths
References
Find this in your own account
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