SSRF occurs when a web application fetches a remote resource based on user-supplied input without validating the destination. If an attacker submits file:///root/.aws/config to a vulnerable URL-preview tool, the server-side code handles the request internally. It reads the local file and echoes the contents back to the attacker’s browser, exposing cloud architecture details. The Severity of Cloud Credential Leaks
: The URL-encoded hexadecimal representation of a colon ( : ).
Let's outline:
Thus, fetch-url-file-3A-2F-2F-2Froot-2F.aws-2Fconfig translates to . fetch-url-file-3A-2F-2F-2Froot-2F.aws-2Fconfig
: The backend application receives the parameter, decodes it, and passes file:///root/.aws/config into its resource-fetching function.
The string fetch-url-file-3A-2F-2F-2Froot-2F.aws-2Fconfig is not just random noise – it is a calculated, encoded attack targeting one of the most sensitive files on a Linux server used for cloud operations. Understanding its structure reveals the attacker’s intent: to perform a local file read via SSRF or LFI, ultimately gaining access to AWS credentials with potentially catastrophic consequences.
When fully decoded and reconstructed into a standard URI scheme, the payload attempts to force the server to execute the following command internally: file:///root/.aws/config The Target: Why Attackers Want .aws/config SSRF occurs when a web application fetches a
The decoded version of this URL-encoded string is fetch-url-file:///root/.aws/config , which targets the sensitive configuration file of the AWS Command Line Interface (CLI) on a Linux system.
The /root/.aws/config file itself might not always contain secrets—but in many real-world misconfigurations, administrators store credentials directly in the config file using the following syntax:
[profile data-mover] s3 = max_concurrent_requests = 100 multipart_chunksize = 50MB The Severity of Cloud Credential Leaks : The
# Vulnerable Python code import requests url = request.GET['url'] response = requests.get(url) # url = file:///root/.aws/config
In a 2022 incident, a bug bounty hunter found a parameter shared_file in a staging server that accepted base64-encoded strings. One string decoded to file:///root/.aws/config . The server returned the config file, which referenced a [prod] profile. The attacker then changed the path to /root/.aws/credentials and exfiltrated valid root keys.