@apostrophecms/file pretty-URL Vulnerable to Unauthenticated SSRF via Host header

ApostropheCMS is an open-source Node.js content management system. In versions up to and including 4.30.0, when `prettyUrls: true` is enabled on `@apostrophecms/file` (a documented SEO feature for serving uploaded files at clean URLs), the public pretty-URL handler builds the upstream URL using the raw `Host` HTTP request header. That URL is then `fetch`'ed and the response body + headers are streamed straight back to the requester. Because `Host` is fully attacker-controlled, an unauthenticated remote attacker can pivot the apostrophe process to issue outbound HTTP requests against any host it can reach on the private network. The path component is constrained to `/uploads/attachments/<cuid>-<slug>.<ext>` (built from a local-DB lookup), which keeps the impact narrow: cross-instance data exfiltration is neutralized by cuid uniqueness, but blind-SSRF residuals remain (network-topology mapping via response-code / timing differences and verbose proxy/WAF 404 body disclosure). As of time of publication, no known patched versions exist.

Source published

12 Jun 2026 20:54:30 UTC

Source modified

15 Jun 2026 18:35:34 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

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CVSS 3.1 · 3.7 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N