DSSRF is a Node.js library that provides a wide range of utilities and advanced SSRF defense checks. Prior to 1.0.5, is_url_safe can treat localhost as safe when DNS resolver 1.1.1.1 returns NXDOMAIN because dns.resolve4 yields no address and no dns.lookup fallback occurs, allowing server-side request forgery. This issue is fixed in version 1.0.5.
Server-Side Request Forgery The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination.