Callback-url-http-3a-2f-2f169.254.169.254-2flatest-2fmeta Data-2fiam-2fsecurity Credentials-2f

Never allow arbitrary URLs in callback parameters. Implement a strict allowlist of approved domains and protocols (e.g., only

Similar patterns have been observed in countless penetration tests and bug bounty reports:

Notes and risks:

The URL in question, http://169.254.169.254/latest/meta-data/iam/security-credentials/ , is an endpoint provided by AWS for instances running within its ecosystem. The IP address 169.254.169.254 is a link-local address that serves as an entry point to the AWS Instance Metadata Service. This service allows AWS instances to access metadata about themselves without the need for explicit configuration. Never allow arbitrary URLs in callback parameters

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The URL http://169.254.169 is a local endpoint accessible only from within an AWS EC2 instance.

An attacker submits this URL-encoded parameter into a web form, API request, or webhook endpoint that takes a user-supplied URL and processes it on the back-end server. This service allows AWS instances to access metadata

The metadata service returns the name of the IAM role.

However, it's crucial to note that the metadata service is accessible only from within the instance itself, ensuring that these credentials are not exposed to external entities. Misconfiguration or exploitation attempts to access this service from outside the instance can be mitigated through proper network and instance configuration.

The string callback-url-http-3A-2F-2F169.254.169.254-2Flatest-2Fmeta data-2Fiam-2Fsecurity credentials-2F is a URL-encoded payload typically used in attacks. It targets the cloud instance metadata service (IMDS) to steal sensitive AWS credentials. What is the AWS Metadata Service? An attacker submits this URL-encoded parameter into a

This change blocks most SSRF attacks because:

: Give your servers only the exact permissions they need to run. To help you secure your systems, let me know: What cloud provider do you use? (AWS, Azure, Google Cloud?) Do you need a code example to block this attack? I can give you exact steps to fix this vulnerability. Share public link

: Use a Web Application Firewall, such as AWS WAF , to block requests containing metadata IP addresses in the query string or body.

Once the vulnerable server makes the request, the attacker reads the response. If the response contains IAM credentials, the attacker wins. Even if the response is not directly returned (e.g., blind SSRF), the attacker can still leverage the credentials by forcing the server to make a request to an attacker‑controlled endpoint, exfiltrating the metadata via DNS or HTTP.