: The URL-encoded schema identifier separating the protocol from the host.
However, IMDSv2 is on older instance types or some AMIs. You must explicitly require it, either at instance launch (metadata options → v2 only ) or by setting the instance metadata service to required .
: You must first perform a PUT request to get a token before you can request metadata.
This specific callback URL is so critical because of the nature of the IAM credentials it exposes. These are , but they are extremely powerful. An attacker who steals these credentials can then run AWS CLI commands from their own machine, performing actions like listing S3 buckets, spinning up new instances, or reading databases, all while appearing as a legitimate service. : The URL-encoded schema identifier separating the protocol
: This is a special IP address known as the link-local address or more specifically in cloud computing, it's used for accessing instance metadata. This IP address is not routable and can only be accessed from within the instance.
The string callback-url-http-3A-2F-2F169.254.169.254-2Flatest-2Fmeta data-2Fiam-2Fsecurity credentials-2F is far from random noise. It is an —a digital signpost pointing directly to one of the most sensitive internal cloud services.
Never trust a user‑supplied URL. Implement a strict allowlist of allowed domains or protocols. If you must fetch arbitrary URLs, use a dedicated “fetch proxy” that: : You must first perform a PUT request
What is 169.254.169.254/latest/meta-data/iam/security-credentials/ ?
If you are writing a post to help others secure their infrastructure against this, consider these key sections: 1. The "Red Flag" Parameters
Common issues with the callback URL include: An attacker who steals these credentials can then
Any process running locally on an EC2 instance can query this IP address without authentication to learn about the instance's environment.
: Force your AWS servers to use tokens. This stops simple SSRF tricks from working.