CVE-2026-53609Public exploitNetwork attack vector

Authorization bypass via prototype pollution

Published Jun 12, 2026 · Updated Jun 12, 2026

Prototype pollution in ApostropheCMS 4.30.0 and earlier allows remote authenticated users to bypass piece-type REST API authorization. apos.util.set() follows attacker-controlled dot-notation segments from PATCH operators without rejecting proto, so assignments reach Object.prototype and supply an inherited publicApiProjection value. Editor-level credentials are required to poison the process; publicApiCheck() then skips its gate for subsequent unauthenticated piece-type requests until restart.

CVSS severity9.1
Critical
EPSS probability0.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Prototype pollution in ApostropheCMS 4.30.0 and earlier allows remote authenticated users to bypass piece-type REST API authorization. apos.util.set() follows attacker-controlled dot-notation segments from PATCH operators without rejecting proto, so assignments reach Object.prototype and supply an inherited publicApiProjection value. Editor-level credentials are required to poison the process; publicApiCheck() then skips its gate for subsequent unauthenticated piece-type requests until restart.

The record

CVE
CVE-2026-53609
Published
Jun 12, 2026
Updated
Jun 12, 2026
Vendor
Apostrophe Technologies
Product
ApostropheCMS
Classifications
CWE-1321, T1190
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jun 12, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 12, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=<= 4.30.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Apostrophe Technologies · ApostropheCMSversion=<= 4.30.0

Published CVSS scores

9.1GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-1321Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
T1190Exploit Public-Facing Application

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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