CVE-2026-75957: CWE-287 Improper Authentication in superdav42 Ultimate Multisite – WordPress Multisite SaaS & WaaS Platform
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.
AI Analysis
Technical Summary
CVE-2026-75957 is an authentication bypass vulnerability in the Ultimate Multisite – WordPress Multisite SaaS & WaaS Platform plugin affecting versions up to 2.15.0. The issue occurs via the `checkout_form` parameter in the `login_customer_after_checkout` function. The publicly accessible AJAX handler `wu_ajax_nopriv_wu_validate_form` accepts a checkout nonce that can be freely obtained. When the parameter `checkout_form=wu-finish-checkout` is used, validation rules are discarded and the request is routed directly into full order processing. The function `maybe_create_customer()` resolves the attacker-supplied email address to an existing WordPress user ID without verifying authentication or ownership. Subsequently, `login_customer_after_checkout()` calls `wp_set_auth_cookie()` for that user ID without requiring a password, allowing attackers to log in as any user, including Network Super Admins. This is exploitable if the targeted user has no existing Ultimate Multisite customer record, such as accounts created before the plugin was configured.
Potential Impact
An unauthenticated attacker can log in as any existing WordPress user, including Network Super Admins, by knowing only the user's email address. This grants full control over the affected WordPress multisite installation, leading to complete compromise of confidentiality, integrity, and availability. The vulnerability is critical with a CVSS score of 9.8, indicating high impact on affected systems.
Mitigation Recommendations
No official patch or fix is currently documented. Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a fix is available, restrict access to the AJAX handler if possible, and monitor for suspicious activity involving the checkout form. Avoid using vulnerable versions and consider disabling the Ultimate Multisite plugin if feasible.
CVE-2026-75957: CWE-287 Improper Authentication in superdav42 Ultimate Multisite – WordPress Multisite SaaS & WaaS Platform
Description
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.
CVSS v3.1
Score 9.8critical
Affected software
superdav42
Ultimate Multisite – WordPress Multisite SaaS & WaaS Platform
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-75957 is an authentication bypass vulnerability in the Ultimate Multisite – WordPress Multisite SaaS & WaaS Platform plugin affecting versions up to 2.15.0. The issue occurs via the `checkout_form` parameter in the `login_customer_after_checkout` function. The publicly accessible AJAX handler `wu_ajax_nopriv_wu_validate_form` accepts a checkout nonce that can be freely obtained. When the parameter `checkout_form=wu-finish-checkout` is used, validation rules are discarded and the request is routed directly into full order processing. The function `maybe_create_customer()` resolves the attacker-supplied email address to an existing WordPress user ID without verifying authentication or ownership. Subsequently, `login_customer_after_checkout()` calls `wp_set_auth_cookie()` for that user ID without requiring a password, allowing attackers to log in as any user, including Network Super Admins. This is exploitable if the targeted user has no existing Ultimate Multisite customer record, such as accounts created before the plugin was configured.
Potential Impact
An unauthenticated attacker can log in as any existing WordPress user, including Network Super Admins, by knowing only the user's email address. This grants full control over the affected WordPress multisite installation, leading to complete compromise of confidentiality, integrity, and availability. The vulnerability is critical with a CVSS score of 9.8, indicating high impact on affected systems.
Mitigation Recommendations
No official patch or fix is currently documented. Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a fix is available, restrict access to the AJAX handler if possible, and monitor for suspicious activity involving the checkout form. Avoid using vulnerable versions and consider disabling the Ultimate Multisite plugin if feasible.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- Wordfence
- Date Reserved
- 2026-08-18T16:14:24.893Z
- Cvss Version
- 3.1
- State
- PUBLISHED
Threat ID: 6abe7484a43b0b3b89bd106e
Added to database: 10/01/2026, 14:56:04 UTC
Last enriched: 10/01/2026, 15:13:17 UTC
Last updated: 10/01/2026, 22:46:09 UTC
Views: 5
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