Vulnerability 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.
CVSS Score
HIGH
Related Weaknesses (CWE)
References
- https://github.com/wpengine/faustjs/commit/cda00de7290f9b178cb1652d30b4cdf5bb868
- https://github.com/wpengine/faustjs/pull/2386
- https://github.com/wpengine/faustjs/security/advisories/GHSA-q6pm-r77q-qcv3
FAQ
What is CVE-2026-54239?
CVE-2026-54239 is a vulnerability with a CVSS score of 8.8 (HIGH). 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 ...
How severe is CVE-2026-54239?
CVE-2026-54239 has been rated HIGH with a CVSS base score of 8.8/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-54239?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.