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

published 2026-06-12 4 mo ago modified 2026-10-25 14 d ago also GHSA-34pj-2622-jvxq , EUVD-2026-36576

cvss: 3.7; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.3%; EPSS 0.3% chance of exploitation in 30 days, percentile 19%
public exploits: 0; none known

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.

Patch / fix

fixed in 1 links 2

npm apostrophe 4.31.0

github.com/apostrophecms/apostrophe@5a88e96 commit
github.com/apostrophecms/apostrophe#5464 pull request

CISA SSVC

Exploitation: Proof of concept is public
Automatable: no
Technical impact: partial
Assessed: 4 mo ago (2026-06-15)

Exploit prediction

0.27% chance of exploitation in the next 30 days, higher than 19% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

github.com https://github.com/apostrophecms/apostrophe/security/advisories/GHSA-34pj-2622-jvxq referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
CNA	3.1	3.7	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
GitHub	3.1	3.7	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

Affected packages

ecosystem	package	affected	fixed in
npm	apostrophe	<4.31.0	4.31.0

Affected products

apostrophecms apostrophe

Classification

Weakness

CWE-918 Server-Side Request Forgery

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary