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CVE-2026-54239

FaustWP — Authentication Bypass via Initialization Vector Modification in Token Envelope

CVSS 3.1 8.8 HIGHCheck source for fixed versionsKEV status unknown

Original advisory

cve-program · CVE-2026-54239

Published

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.

Read the publisher's advisory

Affected versions, risk and source history

cve-program · CVE-2026-54239

Published

faustjs

Vendor product

Publisher's version information

Shown as published. These rules are not interpreted as NuGet package version ranges.

{
                    "vendor": "wpengine",
                    "product": "faustjs",
                    "versions": [
                        {
                            "version": "< 1.8.11",
                            "status": "affected"
                        }
                    ]
                }

Original source record · Cite this exact observation · Complete original publisher JSON