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CVE-2026-53609 apostrophecms CVE debrief

ApostropheCMS, an open-source Node.js content management system, is vulnerable to a critical security issue identified as CVE-2026-53609. This vulnerability affects versions up to and including 4.30.0. The issue arises from the `apos.util.set()` function, which traverses dot-notation paths without properly sanitizing `__proto__`. This oversight allows an authenticated editor to write arbitrary values to `Object.prototype` using the `$pullAll` patch operator. A confirmed gadget in `publicApiCheck()` enables this vulnerability to bypass authorization on all piece-type REST API endpoints for every subsequent unauthenticated request, persisting for the lifetime of the Node.js process. As of the publication date, no patched versions have been identified.

Vendor
apostrophecms
Product
apostrophe
CVSS
CRITICAL 9.1
CISA KEV
Not listed in stored evidence
Original CVE published
2026-06-12
Original CVE updated
2026-06-15
Advisory published
2026-06-12
Advisory updated
2026-06-15

Who should care

Users of ApostropheCMS, particularly those with authenticated editors, should be aware of this critical vulnerability. Its exploitation could lead to significant security breaches, including unauthorized access and data manipulation.

Technical summary

The vulnerability is caused by the improper sanitization of `__proto__` in `apos.util.set()`. This allows attackers to modify `Object.prototype`, which can lead to authorization bypass on REST API endpoints.

Defensive priority

CRITICAL

Recommended defensive actions

  • Apply patches or updates as soon as they become available.
  • Restrict access to authenticated editors and monitor for suspicious activity.
  • Implement additional security measures to protect against potential exploits.

Evidence notes

The CVE-2026-53609 record and associated details can be found at resourceLinkAnnotations: [cve-org, nvd]. Additional information is available at [ref-4].

Sources and references

Verified primary and authoritative sources

  • CVE-2026-53609 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-53609

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-53609 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-53609

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.