CVE-2026-75957

Status: ReceivedCritical (9.8)—

The Ultimate Multisite – WordPress Multisite SaaS & WaaS Platform plugin for WordPress is vulnerable to Authentication Bypass in all versions up to, and including, 2.15.0 via the `checkout_form` parameter of the `login_customer_after_checkout` function.

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This is due to the publicly accessible `wu_ajax_nopriv_wu_validate_form` AJAX handler accepting a freely obtainable checkout nonce, and the `checkout_form=wu-finish-checkout` parameter causing `get_validation_rules()` to discard all validation rules while `finish_checkout_form_fields()` returns an empty step list — forcing `is_last_step()` to return true and routing the request directly into full order processing — after which `maybe_create_customer()` resolves the attacker-supplied `email_address` to an existing WordPress user ID without any authentication or ownership verification, and `login_customer_after_checkout()` calls `wp_set_auth_cookie()` for that user ID via a passwordless code path. This makes it possible for unauthenticated attackers to log in as any existing WordPress user — including a Network Super Admin — simply by knowing their email address. Exploitation requires that the targeted user account has no pre-existing Ultimate Multisite customer record; accounts such as a Network Super Admin on a fresh Multisite install, or any administrator or editor added before Ultimate Multisite was configured, satisfy this condition and are therefore exploitable.

CVSS

Version: 3.1
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Base score: 9.8

Exploitation probability (EPSS)

FIRST hasn't scored this CVE yet (usual for very recent or rejected CVEs).

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

Affected technologies (1)

⚠ AI-inferred from the description — NVD hasn't analyzed this CVE yet, these aren't verified CPEs.

Ultimate Multisite — Ultimate Multisite^AI

CWEs

CWE-287

References

Raw JSON (NVD)

Show

{
  "id": "CVE-2026-75957",
  "cveTags": [],
  "metrics": {
    "cvssMetricV31": [
      {
        "type": "Primary",
        "source": "security@wordfence.com",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 9.8,
          "attackVector": "NETWORK",
          "baseSeverity": "CRITICAL",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
          "integrityImpact": "HIGH",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 5.9,
        "exploitabilityScore": 3.9
      }
    ]
  },
  "affected": [
    {
      "source": "security@wordfence.com",
      "affectedData": [
        {
          "vendor": "superdav42",
          "product": "Ultimate Multisite – WordPress Multisite SaaS & WaaS Platform",
          "versions": [
            {
              "status": "affected",
              "version": "0",
              "versionType": "semver",
              "lessThanOrEqual": "2.15.0"
            }
          ],
          "defaultStatus": "unaffected"
        }
      ]
    }
  ],
  "published": "2026-10-01T08:16:52.763",
  "references": [
    {
      "url": "https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.14.2/inc/checkout/class-checkout.php#L1223",
      "source": "security@wordfence.com"
    },
    {
      "url": "https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.14.2/inc/checkout/class-checkout.php#L208",
      "source": "security@wordfence.com"
    },
    {
      "url": "https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.14.2/inc/checkout/class-checkout.php#L2489",
      "source": "security@wordfence.com"
    },
    {
      "url": "https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.14.2/inc/checkout/class-checkout.php#L2700",
      "source": "security@wordfence.com"
    },
    {
      "url": "https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.14.2/inc/models/class-checkout-form.php#L1352",
      "source": "security@wordfence.com"
    },
    {
      "url": "https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.15.0/inc/checkout/class-checkout.php#L1223",
      "source": "security@wordfence.com"
    },
    {
      "url": "https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.15.0/inc/checkout/class-checkout.php#L208",
      "source": "security@wordfence.com"
    },
    {
      "url": "https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.15.0/inc/checkout/class-checkout.php#L2489",
      "source": "security@wordfence.com"
    },
    {
      "url": "https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.15.0/inc/checkout/class-checkout.php#L2700",
      "source": "security@wordfence.com"
    },
    {
      "url": "https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.15.0/inc/models/class-checkout-form.php#L1352",
      "source": "security@wordfence.com"
    },
    {
      "url": "https://plugins.trac.wordpress.org/changeset/3653622/ultimate-multisite/trunk/inc/checkout/class-checkout.php",
      "source": "security@wordfence.com"
    },
    {
      "url": "https://plugins.trac.wordpress.org/changeset?reponame=&new=3653623%40ultimate-multisite%2Ftags%2F2.15.1&old=3634394%40ultimate-multisite%2Ftags%2F2.15.0",
      "source": "security@wordfence.com"
    },
    {
      "url": "https://www.wordfence.com/threat-intel/vulnerabilities/id/66cb8c6f-d405-4115-a626-040e9b5b1e62?source=cve",
      "source": "security@wordfence.com"
    }
  ],
  "vulnStatus": "Received",
  "weaknesses": [
    {
      "type": "Primary",
      "source": "security@wordfence.com",
      "description": [
        {
          "lang": "en",
          "value": "CWE-287"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "The Ultimate Multisite – WordPress Multisite SaaS & WaaS Platform plugin for WordPress is vulnerable to Authentication Bypass in all versions up to, and including, 2.15.0 via the `checkout_form` parameter of the `login_customer_after_checkout` function. This is due to the publicly accessible `wu_ajax_nopriv_wu_validate_form` AJAX handler accepting a freely obtainable checkout nonce, and the `checkout_form=wu-finish-checkout` parameter causing `get_validation_rules()` to discard all validation rules while `finish_checkout_form_fields()` returns an empty step list — forcing `is_last_step()` to return true and routing the request directly into full order processing — after which `maybe_create_customer()` resolves the attacker-supplied `email_address` to an existing WordPress user ID without any authentication or ownership verification, and `login_customer_after_checkout()` calls `wp_set_auth_cookie()` for that user ID via a passwordless code path. This makes it possible for unauthenticated attackers to log in as any existing WordPress user — including a Network Super Admin — simply by knowing their email address. Exploitation requires that the targeted user account has no pre-existing Ultimate Multisite customer record; accounts such as a Network Super Admin on a fresh Multisite install, or any administrator or editor added before Ultimate Multisite was configured, satisfy this condition and are therefore exploitable."
    }
  ],
  "lastModified": "2026-10-01T08:16:52.763",
  "sourceIdentifier": "security@wordfence.com"
}