Curl-url-http-3a-2f-2f169.254.169.254-2flatest-2fapi-2ftoken !!hot!!

curl http://169.254.169.254/latest/api/token command is essential for initiating a session with the Amazon Web Services (AWS) Instance Metadata Service Version 2 (IMDSv2), providing enhanced security against SSRF attacks. By issuing an HTTP PUT request to this endpoint, instances generate a short-lived, secure token required to access sensitive metadata and IAM credentials, replacing the vulnerable IMDSv1 standard. Read more about this security upgrade on the

This IP is only accessible from within the running EC2 instance itself. It cannot be reached from the public internet or external networks.

Instead, this string is an representation of a command and an internal IP address.

This is the #1 threat vector. Imagine a web application that fetches a URL provided by a user (e.g., a profile picture fetcher).

is the standard method for requesting a session token from the Amazon EC2 Instance Metadata Service Version 2 (IMDSv2). This PUT request, which includes a custom TTL header, initiates a secure session to prevent SSRF vulnerabilities and unauthorized metadata access by requiring token authentication. For more information, visit aws.amazon.com curl-url-http-3A-2F-2F169.254.169.254-2Flatest-2Fapi-2Ftoken

Applications running on the instance can query this service without needing to hardcode credentials or configuration. For example, a web server can automatically discover which security groups it belongs to, or an application can retrieve temporary AWS credentials attached to the instance’s IAM role.

INSTANCE_ID=$(curl -s -H "X-aws-ec2-metadata-token: $METADATA_TOKEN" http://169.254.169.254/latest/meta-data/instance-id)

TOKEN=$(curl -X PUT "http://169.254.169.254/latest/api/token" -H "Content-Type: text/plain") curl -H "X-aws-ec2-metadata-token: $TOKEN" http://169.254.169.254/latest/meta-data/instance-id

INSTANCE_ID=$(metadata_get "meta-data/instance-id") curl http://169

In 2019, Capital One suffered a massive data breach where an attacker exploited a SSRF vulnerability to access a server's metadata. In the older IMDSv1, a single GET request could yield sensitive IAM role credentials. AWS responded by introducing , which requires a "session-oriented" approach: Step 1 : Use a PUT request to generate a temporary token.

In IMDSv1, accessing metadata was a simple HTTP GET request: curl http://169.254.169

: Use that token in the header of subsequent metadata requests. Interesting Blog Posts to Read

The URL-encoded string refers to the AWS EC2 Instance Metadata Service (IMDSv2) token endpoint, which requires a PUT request to generate a session token for secure metadata retrieval. This command is legitimate for administrative tasks but may indicate an SSRF attack attempt if observed in unexpected logs. For more details, visit AWS documentation . EC2 Instance Meta Data Service version 2 (IMDSv2) - GitHub It cannot be reached from the public internet

While convenient, this model introduced severe security vulnerabilities. If an attacker exploited a vulnerability in a web application running on the server, they could trick the application into fetching the metadata—including administrative IAM role credentials—and exfiltrate them. IMDSv2: The Session-Oriented Model

The instance makes a PUT request to /latest/api/token to generate a temporary session token.

curl http://169.254.169.254/latest/meta-data/iam/security-credentials/my-role

Understanding the AWS IMDSv2 Token Request: Securing Cloud Metadata