ApostropheCMS: publicApiProjection Bypass via project Query Builder in Piece-Type REST API

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

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

EPSS

• CVE-2026-33888: 0.51% estimated exploitation activity in the next 30 days; percentile 43.76 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary The getRestQuery method in the @apostrophecms/piece-type module checks whether a MongoDB projection has already been set before applying the admin-configured publicApiProjection. An unauthenticated attacker can supply a project query parameter in the REST API request to pre-populate the projection state, causing the security-enforced publicApiProjection to be skipped entirely. This allows disclosure of fields that the site administrator explicitly restricted from public access. Details When an unauthenticated user queries the piece-type REST API, the getRestQuery method processes the request at modules/@apostrophecms/piece-type/index.js:1120: At [1], applyBuildersSafely iterates over all query string parameters and invokes their corresponding builder methods. The project builder exists in @apostrophecms/doc-type with a launder method (doc-type/index.js:1876) that sanitizes values to booleans: When a request includes ?project[someField]=1, the builder sets query.state.project…

Published by the source

16 Apr 2026, 20:42 UTC

Last modified by the source

16 Apr 2026, 21:11 UTC

Source last checked

26 Oct 2026, 12:48 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-xhq9-58fw-859p

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-xhq9-58fw-859p

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# Patch Next advisory brief: CVE-2026-33888

Advisory: ApostropheCMS: publicApiProjection Bypass via project Query Builder in Piece-Type REST API
IDs: CVE-2026-33888, GHSA-xhq9-58fw-859p
Record: https://patchnext.com/advisories/cve-2026-33888 (revision 2, source checked 26 Oct 2026, 12:48 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: apostrophe 4.29.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm apostrophe: affected < 4.29.0; fixed in 4.29.0

## Suggested inspection (read-only)
- `npm ls apostrophe --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on apostrophe.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-xhq9-58fw-859p (OSV record GHSA-xhq9-58fw-859p lists affected ranges: npm apostrophe >=0 <4.29.0 (fixed))
- Verified: https://github.com/advisories/GHSA-xhq9-58fw-859p (GitHub-reviewed advisory GHSA-xhq9-58fw-859p lists affected ranges: npm apostrophe >=0 <4.29.0)

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