Description
Faust.js is a headless WordPress toolkit. Prior to 1.8.11, the FaustWP WordPress plugin authenticates only the ciphertext in its token envelope and excludes the 16-byte initialization vector from the HMAC in WPE\FaustWP\Auth\encrypt() and WPE\FaustWP\Auth\decrypt() in plugins/faustwp/includes/auth/functions.php. A logged-in non-administrator who obtains an authorization code from GET /generate can modify the unauthenticated initialization vector so that CBC decryption changes the token type and user identifier while the HMAC remains valid. This can produce an access token for an Administrator and permit full WordPress REST API access, administrator-account creation, plugin installation, and arbitrary code execution. This issue is fixed in repository version 1.8.11.
Published: 2026-09-17
Score: 8.8 High
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
AI Analysis

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Remediation

No vendor fix or workaround currently provided.

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History

Fri, 18 Sep 2026 21:30:00 +0000

Type Values Removed Values Added
First Time appeared Wordpress
Wordpress wordpress
Wp Engine
Wp Engine faust.js
Vendors & Products Wordpress
Wordpress wordpress
Wp Engine
Wp Engine faust.js
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}


Thu, 17 Sep 2026 18:45:00 +0000

Type Values Removed Values Added
Description Faust.js is a headless WordPress toolkit. Prior to 1.8.11, the FaustWP WordPress plugin authenticates only the ciphertext in its token envelope and excludes the 16-byte initialization vector from the HMAC in WPE\FaustWP\Auth\encrypt() and WPE\FaustWP\Auth\decrypt() in plugins/faustwp/includes/auth/functions.php. A logged-in non-administrator who obtains an authorization code from GET /generate can modify the unauthenticated initialization vector so that CBC decryption changes the token type and user identifier while the HMAC remains valid. This can produce an access token for an Administrator and permit full WordPress REST API access, administrator-account creation, plugin installation, and arbitrary code execution. This issue is fixed in repository version 1.8.11.
Title FaustWP — Authentication Bypass via Initialization Vector Modification in Token Envelope
Weaknesses CWE-345
CWE-639
References
Metrics cvssV3_1

{'score': 8.8, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'}


Subscriptions

Wordpress Wordpress
Wp Engine Faust.js
cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-09-18T18:33:34.727Z

Reserved: 2026-06-12T16:25:43.084Z

Link: CVE-2026-54239

cve-icon Vulnrichment

Updated: 2026-09-18T17:24:08.989Z

cve-icon NVD

Status : Received

Published: 2026-09-17T19:16:50.047

Modified: 2026-09-18T19:16:42.137

Link: CVE-2026-54239

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-09-19T02:45:16Z

Weaknesses
  • CWE-345

    Insufficient Verification of Data Authenticity

  • CWE-639

    Authorization Bypass Through User-Controlled Key