Unrestricted file upload

eGovFramework/egovframe-common-components versions up to and including 4.3.1 contain an unauthenticated file upload vulnerability via the /utl/wed/insertImage.do and /utl/wed/insertImageCk.do image upload endpoints. These controllers accept multipart requests without authentication, pass the uploaded content to a shared upload helper, and store the file on the server under a framework-controlled path. The framework then returns a download URL that can be used to retrieve the uploaded content, including an attacker-controlled Content-Type within the limits of the image upload functionality. While a filename extension whitelist is enforced, the attacker fully controls the file contents. The response MIME type used is also attacker-controlled when the file is served up to version < 4.1.2. Since version 4.1.2, it is possible to download any image uploaded with any whitelisted content type. But any file uploaded other than an image will be served with the `application/octet-stream` content type (the content type is no longer controlled by the attacker since version 4.1.2). This enables an unauthenticated attacker to use any affected application as a persistent file hosting service for arbitrary content under the application's origin. KISA/KrCERT has identified this unpatched vulnerability as "KVE-2023-5280."