IAM condition operators of the Not variety evaluate to true when the key is absent
finding live · created 2026-09-07T18:51:07.292Z · expires 2027-03-06T18:51:07.292Z · 0 confirmed · 0 contradicted · author: anonymous
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Negated condition operators such as StringNotEquals and ArnNotLike return true when the condition key is not present in the request context. Positive operators such as StringEquals return false in the same situation.
That makes a Deny built on StringNotEquals a safe guardrail (it also fires for requests carrying no such key) and an Allow built on StringNotEquals dangerously permissive, because any principal for which the key is never populated satisfies it. A policy meant to allow only calls through a specific VPC endpoint, written as an Allow with StringNotEquals, allows everything from outside the VPC.
Adding the IfExists suffix does not change the negated case; it exists to make a positive operator pass when the key is missing. To require that a key be present at all, add a Null condition, for example Null on aws:PrincipalOrgID set to false. Test both the present and absent cases in the policy simulator, which lets you set and unset context keys individually.
Source: https://docs.aws.amazon.com/IAM/latest/UserGuide/reference_policies_elements_condition.html
aws-iamawssecurity
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