The POST /api/provider-nodes/validate route in 9router takes a caller-supplied baseUrl and issues server-side HTTP requests to it, guarding the destination with assertPublicUrl from src/shared/utils/ssrfGuard.js. That guard compares hostname strings only: it resolves no DNS, does not revalidate after a redirect, and its IPv4-mapped IPv6 branch is unreachable. The branch matches ^::ffff:(\d+\.\d+\.\d+\.\d+)$, but the WHATWG URL parser canonicalizes such literals to hextets before the guard runs, so new URL("http://[::ffff:127.0.0.1]/").hostname yields [::ffff:7f00:1] and the pattern is tested against a string it is never handed. Every IPv4-mapped address therefore passes, and http://[::ffff:7f00:1] and http://[::ffff:a9fe:a9fe] reach loopback and link-local metadata addresses; a hostname whose A record points at an internal address passes as well because no resolution occurs. In the custom-embedding branch the upstream response body is truncated to 200 bytes and returned to the caller w

The POST /api/provider-nodes/validate route in 9router takes a caller-supplied baseUrl and issues server-side HTTP requests to it, guarding the destination with assertPublicUrl from src/shared/utils/ssrfGuard.js. That guard compares hostname strings only: it resolves no DNS, does not revalidate after a redirect, and its IPv4-mapped IPv6 branch is unreachable. The branch matches ^::ffff:(\d+\.\d+\.\d+\.\d+)$, but the WHATWG URL parser canonicalizes such literals to hextets before the guard runs, so new URL("http://[::ffff:127.0.0.1]/").hostname yields [::ffff:7f00:1] and the pattern is tested against a string it is never handed. Every IPv4-mapped address therefore passes, and http://[::ffff:7f00:1] and http://[::ffff:a9fe:a9fe] reach loopback and link-local metadata addresses; a hostname whose A record points at an internal address passes as well because no resolution occurs. In the custom-embedding branch the upstream response body is truncated to 200 bytes and returned to the calle...