{"id":"CVE-2026-75957","aliases":[],"url":"https://o3.security/vulnerability/CVE-2026-75957","summary":"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`…","details":"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.","published":"2026-10-01T07:40:23.541Z","modified":"2026-10-01T13:42:37.093Z","cvss":{"score":9.8,"severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[],"fix":null,"references":[{"type":"WEB","url":"https://www.wordfence.com/threat-intel/vulnerabilities/id/66cb8c6f-d405-4115-a626-040e9b5b1e62?source=cve"},{"type":"WEB","url":"https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.15.0/inc/checkout/class-checkout.php#L2489"},{"type":"WEB","url":"https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.15.0/inc/checkout/class-checkout.php#L1223"},{"type":"WEB","url":"https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.15.0/inc/checkout/class-checkout.php#L2700"},{"type":"WEB","url":"https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.15.0/inc/models/class-checkout-form.php#L1352"},{"type":"WEB","url":"https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.15.0/inc/checkout/class-checkout.php#L208"},{"type":"WEB","url":"https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.14.2/inc/checkout/class-checkout.php#L2489"},{"type":"WEB","url":"https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.14.2/inc/checkout/class-checkout.php#L1223"},{"type":"WEB","url":"https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.14.2/inc/checkout/class-checkout.php#L2700"},{"type":"WEB","url":"https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.14.2/inc/models/class-checkout-form.php#L1352"},{"type":"WEB","url":"https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.14.2/inc/checkout/class-checkout.php#L208"},{"type":"WEB","url":"https://plugins.trac.wordpress.org/changeset?reponame=&new=3653623%40ultimate-multisite%2Ftags%2F2.15.1&old=3634394%40ultimate-multisite%2Ftags%2F2.15.0"},{"type":"WEB","url":"https://plugins.trac.wordpress.org/changeset/3653622/ultimate-multisite/trunk/inc/checkout/class-checkout.php"}],"provenance":{"sources":["OSV.dev","NVD","FIRST.org (EPSS)"],"lastVerified":"2026-10-01T13:42:37.093Z"}}