CVE-2026-75957

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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 \u2014 forcing `is_last_step()` to return true and routing the request directly into full order processing \u2014 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 \u2014 including a Network Super Admin \u2014 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."}], "title": "Ultimate Multisite <= 2.15.0 - Unauthenticated Authentication Bypass via 'checkout_form' Parameter", "references": [{"url": "https://www.wordfence.com/threat-intel/vulnerabilities/id/66cb8c6f-d405-4115-a626-040e9b5b1e62?source=cve"}, {"url": "https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.15.0/inc/checkout/class-checkout.php#L2489"}, {"url": "https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.15.0/inc/checkout/class-checkout.php#L1223"}, {"url": "https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.15.0/inc/checkout/class-checkout.php#L2700"}, {"url": "https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.15.0/inc/models/class-checkout-form.php#L1352"}, {"url": "https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.15.0/inc/checkout/class-checkout.php#L208"}, {"url": "https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.14.2/inc/checkout/class-checkout.php#L2489"}, {"url": "https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.14.2/inc/checkout/class-checkout.php#L1223"}, {"url": "https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.14.2/inc/checkout/class-checkout.php#L2700"}, {"url": "https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.14.2/inc/models/class-checkout-form.php#L1352"}, {"url": "https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.14.2/inc/checkout/class-checkout.php#L208"}, {"url": "https://plugins.trac.wordpress.org/changeset?reponame=&new=3653623%40ultimate-multisite%2Ftags%2F2.15.1&old=3634394%40ultimate-multisite%2Ftags%2F2.15.0"}, {"url": "https://plugins.trac.wordpress.org/changeset/3653622/ultimate-multisite/trunk/inc/checkout/class-checkout.php"}], "problemTypes": [{"descriptions": [{"lang": "en", "description": "CWE-287 Improper Authentication", "cweId": "CWE-287", "type": "CWE"}]}], "metrics": [{"cvssV3_1": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "baseScore": 9.8, "baseSeverity": "CRITICAL"}}], "credits": [{"lang": "en", "type": "finder", "value": "zickzick2"}], "timeline": [{"time": "2026-08-18T20:33:59.000Z", "lang": "en", "value": "Vendor Notified"}, {"time": "2026-09-30T19:18:17.000Z", "lang": "en", "value": "Disclosed"}]}, "adp": [{"metrics": [{"other": {"type": "ssvc", "content": {"timestamp": "2026-10-01T13:40:29.024281Z", "id": "CVE-2026-75957", "options": [{"Exploitation": "none"}, {"Automatable": "yes"}, {"Technical Impact": "total"}], "role": "CISA Coordinator", "version": "2.0.3"}}}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-10-01T13:42:37.093Z"}}]}}

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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 \u2014 forcing `is_last_step()` to return true and routing the request directly into full order processing \u2014 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 \u2014 including a Network Super Admin \u2014 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."}], "problemTypes": [{"descriptions": [{"lang": "en", "type": "CWE", "cweId": "CWE-287", "description": "CWE-287 Improper Authentication"}]}], "providerMetadata": {"orgId": "b15e7b5b-3da4-40ae-a43c-f7aa60e62599", "shortName": "Wordfence", "dateUpdated": "2026-10-01T07:40:23.541Z"}}}, "cveMetadata": {"cveId": "CVE-2026-75957", "state": "PUBLISHED", "dateUpdated": "2026-10-01T13:42:37.093Z", "dateReserved": "2026-08-18T16:14:24.893Z", "assignerOrgId": "b15e7b5b-3da4-40ae-a43c-f7aa60e62599", "datePublished": "2026-10-01T07:40:23.541Z", "assignerShortName": "Wordfence"}, "dataVersion": "5.2"}

{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "product": "Ultimate Multisite \u2013 WordPress Multisite SaaS & WaaS Platform", "vendor": "superdav42", "versions": [{"lessThanOrEqual": "2.15.0", "status": "affected", "version": "0", "versionType": "semver"}]}], "source": "security@wordfence.com"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "The Ultimate Multisite \u2013 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 \u2014 forcing `is_last_step()` to return true and routing the request directly into full order processing \u2014 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 \u2014 including a Network Super Admin \u2014 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."}], "id": "CVE-2026-75957", "lastModified": "2026-10-01T14:17:30.497", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "HIGH", "baseScore": 9.8, "baseSeverity": "CRITICAL", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 5.9, "source": "security@wordfence.com", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-75957", "options": [{"exploitation": "none"}, {"automatable": "yes"}, {"technicalImpact": "total"}], "role": "CISA Coordinator", "timestamp": "2026-10-01T13:40:29.024281Z", "version": "2.0.3"}}]}, "published": "2026-10-01T08:16:52.763", "references": [{"source": "security@wordfence.com", "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"}], "sourceIdentifier": "security@wordfence.com", "vulnStatus": "Deferred", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-287"}], "source": "security@wordfence.com", "type": "Secondary"}]}

{}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[0,2.15.0]"}}], "enrichment": {"confidence": 95.0, "confidence_source": "inferred", "scores": [{"score": 95.0, "source": "inferred"}]}, "product": "ultimate_multisite", "vendor": "superdav42"}, {"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[0,2.15.0]"}}], "enrichment": {"confidence": 90.0, "confidence_source": "inferred", "scores": [{"score": 90.0, "source": "inferred"}]}, "product": "ultimate_multisite", "vendor": "wordpress-extensions"}], "created": "2026-10-01T10:45:07.717045+00:00", "updated": "2026-10-01T15:36:40.069656+00:00", "vendors": ["superdav42", "superdav42$PRODUCT$ultimate_multisite", "wordpress-extensions", "wordpress-extensions$PRODUCT$ultimate_multisite"]}