Callback-url-file-3a-2f-2f-2fhome-2f-2a-2f.aws-2fcredentials

Encoded URL: callback-url-file-3A-2F-2F-2Fhome-2F-2A-2F.aws-2Fcredentials

protocol to trick an application into reading local files instead of fetching a remote URL. If the application has enough permissions, it may return the contents of the AWS credentials file, exposing: Access Key IDs Secret Access Keys Session Tokens 🛡️ How to Protect Your Infrastructure Validate Protocol Schemes : Only allow for callback URLs. Explicitly block Use an Allowlist callback-url-file-3A-2F-2F-2Fhome-2F-2A-2F.aws-2Fcredentials

Callback Acknowledgment

• Even though it’s a file write, the auth server expects a confirmation (e.g., 200 OK over a dummy HTTP or via log entry).

• The .aws/credentials file is the standard location for AWS CLI credentials (access key ID and secret access key). If accessed by an attacker or inadvertently sent to a remote callback endpoint, it enables unauthorized access to AWS resources.
• Any mechanism that constructs callbacks including file:/// URIs pointing at ~/.aws/credentials risks credential leakage, privilege escalation, and account compromise.
• Wildcard (* or similar) suggests an attempt to enumerate multiple users' home directories or to be used in patterns for scanning.

• Outbound connections from internal hosts to unusual external endpoints following user actions.
• Application logs showing fetches of file:/// URLs or requests containing callback-url-file-encoded strings.
• Unexpected process reading ~/.aws/credentials (audit logs, eBPF, or file access monitoring).
• Presence of percent-encoded file-URI strings in logs, config files, database entries, or webhooks.
• New API keys in use from unknown IPs, or IAM activity from unusual locations.

Instead of passing a callback URL with local paths, use an AWS SDK (like Boto3 for Python or the JavaScript SDK) to initialize a client. The SDK will automatically look for your credentials at ~/.aws/credentials without needing a URL. Encoded URL: callback-url-file-3A-2F-2F-2Fhome-2F-2A-2F

file://: The URI scheme used to access files on the local host. Even though it’s a file write, the auth

Sample article outline for the correct topic: "Preventing SSRF attacks that target AWS credentials"

Title: The $100,000 Mistake: How a file:// callback path exposes your AWS keys