CVE-2026-53607: 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…

PriorityP419low3.7CVSS 3.1

AVNACHPRNUINSUCLINAN

EPSS

0.23%

13.6th percentile

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/-.` (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.

Affected

2 ranges

Vendor	Product	Version range	Fixed in
apostrophecms	apostrophe	<= 4.30.0	—
apostrophecms	apostrophe	>= 0 < 4.31.0	4.31.0

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