CVE-2026-54239

HIGHPre-NVD 8.88.8—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 8.8 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.2%, top 89% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
Trending — 3 sources updated this week
8.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 8.8Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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 v3
8.8
EG Score
8.8(medium)
EG Risk
40(Track)
EG Risk 40/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity88% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
11%
KEV
Not listed

Published

September 17, 2026

Last Modified

September 18, 2026

Advisory Details (3)

Auto-updated Sep 17, 2026
Patch available. Sources: github, github_pr, github_commit.
github_commit Patch Available

commit cda00de7290f (wpengine/faustjs)

Patch available: wpengine/faustjs @faustwp/[email protected] (contains commit cda00de7290f)

https://github.com/wpengine/faustjs/commit/cda00de7290f9b178cb1652d30b4cdf5bb8688d0
github_pr Patch Available

fix(faustwp): include IV in token envelope HMAC (GHSA-q6pm-r77q-qcv3)

Patch available: wpengine/faustjs @faustwp/[email protected] (PR #2386 merged 2026-06-03)

https://github.com/wpengine/faustjs/pull/2386
github Patch Available

FaustWP through 1.8.0 — Authentication Bypass via Initialization Vector Modification in Token Envelope · Advisory · wpengine/faustjs · GitHub

https://github.com/wpengine/faustjs/security/advisories/GHSA-q6pm-r77q-qcv3

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 7× in last 7d / 7× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-09-19 21:46 UTCEG score recompute
  2. 2026-09-18 19:28 UTCEG score recompute
  3. 2026-09-18 19:28 UTCEPSS rescore
  4. 2026-09-18 18:44 UTCEG score recompute
  5. 2026-09-17 19:26 UTCEG score recompute
  6. 2026-09-17 18:43 UTCEG score recompute
  7. 2026-09-17 18:39 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-54239?
CVE-2026-54239 is a high vulnerability published on September 17, 2026. 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…
When was CVE-2026-54239 disclosed?
CVE-2026-54239 was first published in the National Vulnerability Database on September 17, 2026, with the most recent update on September 18, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-54239 actively exploited?
CVE-2026-54239 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 88.7% of all scored CVEs.
What is the CVSS score of CVE-2026-54239?
CVE-2026-54239 has a CVSS v3 base score of 8.8 (NVD).
How do I remediate CVE-2026-54239?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-54239, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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