{"id":"CVE-2026-75957","published":"2026-10-01T08:16:52.763","lastModified":"2026-10-01T14:17:30.497","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.","cvssScore":9.8,"cvssSeverity":"CRITICAL","cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","cwes":["CWE-287"],"vendors":[],"products":[],"references":[{"url":"https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.14.2/inc/checkout/class-checkout.php#L1223","tags":[]},{"url":"https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.14.2/inc/checkout/class-checkout.php#L208","tags":[]},{"url":"https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.14.2/inc/checkout/class-checkout.php#L2489","tags":[]},{"url":"https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.14.2/inc/checkout/class-checkout.php#L2700","tags":[]},{"url":"https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.14.2/inc/models/class-checkout-form.php#L1352","tags":[]},{"url":"https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.15.0/inc/checkout/class-checkout.php#L1223","tags":[]},{"url":"https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.15.0/inc/checkout/class-checkout.php#L208","tags":[]},{"url":"https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.15.0/inc/checkout/class-checkout.php#L2489","tags":[]},{"url":"https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.15.0/inc/checkout/class-checkout.php#L2700","tags":[]},{"url":"https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.15.0/inc/models/class-checkout-form.php#L1352","tags":[]},{"url":"https://plugins.trac.wordpress.org/changeset/3653622/ultimate-multisite/trunk/inc/checkout/class-checkout.php","tags":[]},{"url":"https://plugins.trac.wordpress.org/changeset?reponame=&new=3653623%40ultimate-multisite%2Ftags%2F2.15.1&old=3634394%40ultimate-multisite%2Ftags%2F2.15.0","tags":[]},{"url":"https://www.wordfence.com/threat-intel/vulnerabilities/id/66cb8c6f-d405-4115-a626-040e9b5b1e62?source=cve","tags":[]}],"exploitRefs":[],"hasPoc":false,"ai":{"summary":"The Ultimate Multisite plugin for WordPress allows unauthenticated attackers to bypass authentication and log in as any existing user, including Network Super Admins, by exploiting a flaw in the `checkout_form` parameter.","exploitability":"Exploitation requires knowledge of the targeted user's email address and a checkout nonce, making it moderately hard to exploit.","blast_radius":"If exploited, this flaw could grant full access to any existing WordPress user account, potentially leading to complete compromise of the WordPress site or network.","remediation":"Disable the affected feature or upgrade to version 2.15.1 or later.","detection":"No reliable host or network indicator is derivable from the published description.","tags":["auth-bypass","web","wp-plugin"],"model":"qwen2.5:7b-instruct","analyzedAt":"2026-10-02T08:41:32.986Z"}}