High 8.8Published Sep 17, 2026

CVE-2026-54239FaustWP — Authentication Bypass via Initialization Vector Modification in Token Envelope

Updated under an hour ago (2026-10-19 09:40 UTC)

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It affects wpengine faustjs. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Every CVE for wpengine faustjs

Exploited in the last 30 days

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.

CVSS: 8.8 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Weakness (CWE): CWE-345, CWE-639
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Awaiting Analysis
Record last updated: Sep 18, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

wpengine faustjs wpengine:faustjs (from the name)	before 1.8.11	CNA record

References

https://github.com/wpengine/faustjs/security/advisories/GHSA-q6pm-r77q-qcv3x-refsource-confirm
https://github.com/wpengine/faustjs/pull/2386x-refsource-misc
https://github.com/wpengine/faustjs/commit/cda00de7290f9b178cb1652d30b4cdf5bb8688d0x-refsource-misc

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.