Curl-url-file-3a-2f-2f-2f |best|

curl -X POST -F "file=@localfile.txt" http://example.com/upload

The server decodes this to file:///etc/passwd and, if no protocol whitelist exists, reads local files. The appearance of -3A-2F-2F-2F in logs is a suggesting an attempted SSRF or directory traversal attack. curl-url-file-3A-2F-2F-2F

On Windows, the syntax can include drive letters, such as file:///C:/Users/name/file.txt . Security Risks: Arbitrary File Read and SSRF curl -X POST -F "file=@localfile

Browsers often have strict (Cross-Origin Resource Sharing) policies that prevent local files from making certain requests. Using curl file:/// allows you to interact with local files in a "clean, policy-free testing environment" that bypasses these browser-enforced restrictions. Security Risks: Arbitrary File Read and SSRF Browsers

, which is the standard URI scheme for accessing local files on a computer. Common Use Cases for curl file:///

The existence of the file:/// protocol in curl highlights the thin line between functionality and vulnerability. While documentation from ReqBin emphasizes the utility of curl for downloading data, security professionals view these same features as potential exploit vectors.