Admidio Vulnerable to SSRF and Local File Read via Unrestricted URL Fetch in SSO Metadata Endpoint

Admidio is an open-source user management solution. In versions 5.0.0 through 5.0.6, unrestricted URL fetch in the SSO Metadata API can result in SSRF and local file reads. The SSO Metadata fetch endpoint at modules/sso/fetch_metadata.php accepts an arbitrary URL via $_GET['url'], validates it only with PHP's FILTER_VALIDATE_URL, and passes it directly to file_get_contents(). FILTER_VALIDATE_URL accepts file://, http://, ftp://, data://, and php:// scheme URIs. An authenticated administrator can use this endpoint to read arbitrary local files via the file:// wrapper (Local File Read), reach internal services via http:// (SSRF), or fetch cloud instance metadata. The full response body is returned verbatim to the caller. This issue has been fixed in version 5.0.7.