The /api/templates/fetch endpoint accepts a caller-supplied url parameter and performs a server-side HTTP GET request to that URL without authentication and without URL scheme or host validation. The server's response is returned directly to the caller. type. This constitutes an unauthenticated SSRF vulnerability affecting any publicly reachable Arcane instance.
Response handling produces four distinct outcomes observable by the caller:
"Invalid JSON response: invalid character '<'...")"connection refused") and filtered ones ("i/o timeout")Send an unauthenticated GET request to /api/templates/fetch, passing the target URL as the url query parameter.
{
"cwe_ids": [
"CWE-918"
],
"github_reviewed": true,
"github_reviewed_at": "2026-04-10T20:59:27Z",
"nvd_published_at": "2026-04-10T21:16:27Z",
"severity": "HIGH"
}