What is SSRF, and how can attackers exploit it to access AWS instance metadata and credentials? Learn how Server-Side Request Forgery enables unauthorized internal requests—critical for CompTIA Security+ (Plus) SY0-701 exam success.
Table of Contents
Question
A web application allows users to input a URL, which the server fetches and displays. An attacker enters http://169.254.169.254/latest/meta-data/, exposing AWS credentials. Which vulnerability is this?
A. Path traversal
B. IDOR
C. DNS spoofing
D. SSRF
E. LFI
Answer
D. SSRF
Explanation
SSRF tricks the server into making internal requests (e.g., accessing AWS metadata or private APIs).
The vulnerability exploited when a web application allows users to input a URL, which the server fetches and displays—enabling attackers to access http://169.254.169.254/latest/meta-data/ and expose AWS credentials—is Server-Side Request Forgery (SSRF).
SSRF occurs when an attacker manipulates a vulnerable web application to make HTTP requests to internal or external resources on behalf of the server, often bypassing network access controls and exposing sensitive data.
In cloud environments like AWS, the metadata service is accessible only from within the instance at the special IP address 169.254.169.254. This service provides configuration details and, critically, IAM credentials if the instance has an assigned role.
Attackers exploit SSRF by submitting a URL pointing to this metadata endpoint. If the application fetches and returns the response, the attacker can retrieve sensitive information such as AWS access keys and tokens, which can be used to escalate privileges or compromise cloud resources.
This attack is particularly dangerous in AWS environments using IMDSv1, which lacks authentication, making it easy for SSRF to succeed. IMDSv2 mitigates this risk by requiring session tokens for access.
Real-world incidents have shown attackers systematically probing for SSRF vulnerabilities and exfiltrating AWS credentials using various URL parameters and subpaths.
Server-Side Request Forgery (SSRF) lets attackers trick the server into making internal requests, such as to the AWS metadata endpoint, exposing sensitive credentials and configuration data.
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