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CVE-2026-54239 (GCVE-0-2026-54239)

Vulnerability from cvelistv5 – Published: 2026-09-17 18:25 – Updated: 2026-09-17 18:25
VLAI
Title
FaustWP — Authentication Bypass via Initialization Vector Modification in Token Envelope
Summary
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.
Severity
8.8 (High)
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CWE
  • CWE-345 - Insufficient Verification of Data Authenticity
  • CWE-639 - Authorization Bypass Through User-Controlled Key
Assigner
References
Impacted products
Vendor Product Version CPE status
wpengine faustjs Affected: < 1.8.11
guessed Create a notification for this product.
Show details on NVD website
To clipboard 

{
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      "affected": [
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          "product": "faustjs",
          "vendor": "wpengine",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 1.8.11"
            }
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      "descriptions": [
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          "lang": "en",
          "value": "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."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 8.8,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "HIGH",
            "integrityImpact": "HIGH",
            "privilegesRequired": "LOW",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-345",
              "description": "CWE-345: Insufficient Verification of Data Authenticity",
              "lang": "en",
              "type": "CWE"
            }
          ]
        },
        {
          "descriptions": [
            {
              "cweId": "CWE-639",
              "description": "CWE-639: Authorization Bypass Through User-Controlled Key",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-17T18:25:36.503Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/wpengine/faustjs/security/advisories/GHSA-q6pm-r77q-qcv3",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/wpengine/faustjs/security/advisories/GHSA-q6pm-r77q-qcv3"
        },
        {
          "name": "https://github.com/wpengine/faustjs/pull/2386",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/wpengine/faustjs/pull/2386"
        },
        {
          "name": "https://github.com/wpengine/faustjs/commit/cda00de7290f9b178cb1652d30b4cdf5bb8688d0",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/wpengine/faustjs/commit/cda00de7290f9b178cb1652d30b4cdf5bb8688d0"
        }
      ],
      "source": {
        "advisory": "GHSA-q6pm-r77q-qcv3",
        "discovery": "UNKNOWN"
      },
      "title": "FaustWP  \u2014 Authentication Bypass via Initialization Vector Modification in Token Envelope"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-54239",
    "datePublished": "2026-09-17T18:25:36.503Z",
    "dateReserved": "2026-06-12T16:25:43.084Z",
    "dateUpdated": "2026-09-17T18:25:36.503Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "nvd": {
      "cve": {
        "affected": [
          {
            "affectedData": [
              {
                "product": "faustjs",
                "vendor": "wpengine",
                "versions": [
                  {
                    "status": "affected",
                    "version": "\u003c 1.8.11"
                  }
                ]
              }
            ],
            "source": "security-advisories@github.com"
          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "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."
          }
        ],
        "id": "CVE-2026-54239",
        "lastModified": "2026-09-17T19:16:50.047",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "NETWORK",
                "availabilityImpact": "HIGH",
                "baseScore": 8.8,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "LOW",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
                "version": "3.1"
              },
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              "impactScore": 5.9,
              "source": "security-advisories@github.com",
              "type": "Secondary"
            }
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        },
        "published": "2026-09-17T19:16:50.047",
        "references": [
          {
            "source": "security-advisories@github.com",
            "url": "https://github.com/wpengine/faustjs/commit/cda00de7290f9b178cb1652d30b4cdf5bb8688d0"
          },
          {
            "source": "security-advisories@github.com",
            "url": "https://github.com/wpengine/faustjs/pull/2386"
          },
          {
            "source": "security-advisories@github.com",
            "url": "https://github.com/wpengine/faustjs/security/advisories/GHSA-q6pm-r77q-qcv3"
          }
        ],
        "sourceIdentifier": "security-advisories@github.com",
        "vulnStatus": "Received",
        "weaknesses": [
          {
            "description": [
              {
                "lang": "en",
                "value": "CWE-345"
              },
              {
                "lang": "en",
                "value": "CWE-639"
              }
            ],
            "source": "security-advisories@github.com",
            "type": "Primary"
          }
        ]
      }
    }
  }
}



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