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CVE-2026-75957— Ultimate Multisite <= 2.15.0 - Unauthenticated Authentication Bypass via 'checkout_form' Parameter

Quick assessment

Affected
superdav42 Ultimate Multisite – WordPress Multisite SaaS & WaaS Platform
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

WordPress 插件 “The Ultimate Multisite – WordPress Multisite SaaS & WaaS Platform” 在包括 2.15.0 在内的所有版本中均存在身份验证绕过漏洞。该漏洞可通过 函数中的 参数被利用。 漏洞成因如下：公开可访问的 AJAX 处理程序 接受一个可自由获取的结账 nonce（一次性令牌）。当请求中包含 参数时， 函数会丢弃所有验证规则，同时 返回一个空的步骤列表。这导致 函数强制返回 true，从而将请求直接路由至完整的订单处理流程。随后， 函

CVSS 9.8 · Critical

Possible ATT&CK Techniques 1 AI

T1078 · Valid Accounts
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I. Basic Information for CVE-2026-75957

Vulnerability Information
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Vulnerability Title
Ultimate Multisite <= 2.15.0 - Unauthenticated Authentication Bypass via 'checkout_form' Parameter
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
认证机制不恰当
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
superdav42 Ultimate Multisite – WordPress Multisite SaaS & WaaS Platform 0 ~ 2.15.0 -

II. Public POCs for CVE-2026-75957

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III. Intelligence Information for CVE-2026-75957

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Patches & Fixes for CVE-2026-75957 (1)

Vendor Advisories for CVE-2026-75957 (1)

IV. Related Vulnerabilities

Same weakness: CWE-287

V. Comments for CVE-2026-75957

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