Ultimate Multisite <= 2.15.0 - Unauthenticated Authentication Bypass via 'checkout_form' Parameter

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-75957
StatePUBLISHED
AssignerWordfence
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-01 08:16:52 UTC
Updated2026-10-01 14:17:30 UTC
DescriptionThe 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.

Risk And Classification

Primary CVSS: v3.1 9.8 CRITICAL from [email protected]

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Problem Types: CWE-287 | CWE-287 CWE-287 Improper Authentication

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary9.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
3.1CNADECLARED9.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Superdav42 Ultimate Multisite WordPress Multisite SaaS WaaS Platform affected 2.15.0 semver Not specified

References

ReferenceSourceLinkTags
plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.14.2/inc/checkout/class-che... [email protected] plugins.trac.wordpress.org
plugins.trac.wordpress.org/changeset/3653622/ultimate-multisite/trunk/inc/checkout/class... [email protected] plugins.trac.wordpress.org
plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.14.2/inc/checkout/class-che... [email protected] plugins.trac.wordpress.org
plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.15.0/inc/models/class-check... [email protected] plugins.trac.wordpress.org
plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.15.0/inc/checkout/class-che... [email protected] plugins.trac.wordpress.org
plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.15.0/inc/checkout/class-che... [email protected] plugins.trac.wordpress.org
plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.14.2/inc/checkout/class-che... [email protected] plugins.trac.wordpress.org
www.wordfence.com/threat-intel/vulnerabilities/id/66cb8c6f-d405-4115-a626-040e9... [email protected] www.wordfence.com
plugins.trac.wordpress.org/changeset [email protected] plugins.trac.wordpress.org
plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.14.2/inc/models/class-check... [email protected] plugins.trac.wordpress.org
plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.15.0/inc/checkout/class-che... [email protected] plugins.trac.wordpress.org
plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.14.2/inc/checkout/class-che... [email protected] plugins.trac.wordpress.org
plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.15.0/inc/checkout/class-che... [email protected] plugins.trac.wordpress.org
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: zickzick2 (en)

Additional Advisory Data

SourceTimeEvent
CNA2026-08-18T20:33:59.000ZVendor Notified
CNA2026-09-30T19:18:17.000ZDisclosed

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