Apostrophe has Server-Side Prototype Pollution in apos.util.set via patch operators that leads to process-wide authorization bypass

published 2026-06-12 4 mo ago modified 2026-10-25 14 d ago also GHSA-6h5j-32cf-4253 , EUVD-2026-36590

cvss: 9.1; 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 28%
public exploits: 0; none known

ApostropheCMS is an open-source Node.js content management system. In versions up to and including 4.30.0, `apos.util.set()` traverses dot-notation paths without sanitizing `__proto__`, allowing an authenticated editor to write arbitrary values to `Object.prototype` via the `$pullAll` patch operator. A confirmed gadget in `publicApiCheck()` causes this to bypass authorization on all piece-type REST API endpoints for every subsequent unauthenticated request, for the lifetime of the Node.js process. As of time of publication, no known patched versions are available.

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

0.35% chance of exploitation in the next 30 days, higher than 28% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

github.com https://github.com/apostrophecms/apostrophe/security/advisories/GHSA-6h5j-32cf-4253 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
CNA	3.1	9.1	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:L
GitHub	3.1	9.1	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:L

Affected packages

ecosystem	package	affected	fixed in
npm	apostrophe	<4.31.0	4.31.0

Affected products

apostrophecms apostrophe

Classification

Weakness

CWE-1321 Improperly Controlled Modification of Object Prototype Attributes

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