{"schemaVersion":3,"id":"CVE-2026-75957","aliases":[],"status":"published","duplicateOf":null,"title":null,"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.","dates":{"published":"2026-10-01T07:40:23.541Z","modified":"2026-10-01T13:42:37.093Z","reserved":null,"kevAdded":[],"kevDue":[]},"cvss":{"headline":{"score":9.8,"severity":"critical","version":"3.1","versionLabel":"v3.1","source":"CVE.org","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","computed":false,"selection":"backend-summary"},"metrics":[{"version":"3.1","versionLabel":"v3.1","source":"CVE.org","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","exploitability":null,"impact":null,"computed":false},{"version":"3.1","versionLabel":"v3.1","source":"NVD","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","exploitability":null,"impact":null,"computed":false},{"version":"3.1","versionLabel":"v3.1","source":"wordfence","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","exploitability":null,"impact":null,"computed":false}]},"epss":{"probability":0.00576,"percentile":0.46474,"severity":"low","asOf":"2026-10-20T00:00:00.000Z","change":{"pp":null,"baselineDate":null,"baselineScore":null},"history":[{"date":"2026-10-02T00:00:00.000Z","score":0.00576,"percentile":null},{"date":"2026-10-03T00:00:00.000Z","score":0.00576,"percentile":null},{"date":"2026-10-04T00:00:00.000Z","score":0.00576,"percentile":null},{"date":"2026-10-05T00:00:00.000Z","score":0.00576,"percentile":null},{"date":"2026-10-06T00:00:00.000Z","score":0.00576,"percentile":null},{"date":"2026-10-07T00:00:00.000Z","score":0.00576,"percentile":null},{"date":"2026-10-08T00:00:00.000Z","score":0.00576,"percentile":null},{"date":"2026-10-09T00:00:00.000Z","score":0.00576,"percentile":null},{"date":"2026-10-10T00:00:00.000Z","score":0.00576,"percentile":null},{"date":"2026-10-11T00:00:00.000Z","score":0.00576,"percentile":null},{"date":"2026-10-12T00:00:00.000Z","score":0.00576,"percentile":null},{"date":"2026-10-13T00:00:00.000Z","score":0.00576,"percentile":null},{"date":"2026-10-14T00:00:00.000Z","score":0.00576,"percentile":null},{"date":"2026-10-15T00:00:00.000Z","score":0.00576,"percentile":null},{"date":"2026-10-16T00:00:00.000Z","score":0.00576,"percentile":null},{"date":"2026-10-17T00:00:00.000Z","score":0.00576,"percentile":null},{"date":"2026-10-18T00:00:00.000Z","score":0.00576,"percentile":null},{"date":"2026-10-19T00:00:00.000Z","score":0.00576,"percentile":null},{"date":"2026-10-20T00:00:00.000Z","score":0.00576,"percentile":0.46474}],"last30":[{"date":"2026-10-02T00:00:00.000Z","score":0.00576,"percentile":null},{"date":"2026-10-03T00:00:00.000Z","score":0.00576,"percentile":null},{"date":"2026-10-04T00:00:00.000Z","score":0.00576,"percentile":null},{"date":"2026-10-05T00:00:00.000Z","score":0.00576,"percentile":null},{"date":"2026-10-06T00:00:00.000Z","score":0.00576,"percentile":null},{"date":"2026-10-07T00:00:00.000Z","score":0.00576,"percentile":null},{"date":"2026-10-08T00:00:00.000Z","score":0.00576,"percentile":null},{"date":"2026-10-09T00:00:00.000Z","score":0.00576,"percentile":null},{"date":"2026-10-10T00:00:00.000Z","score":0.00576,"percentile":null},{"date":"2026-10-11T00:00:00.000Z","score":0.00576,"percentile":null},{"date":"2026-10-12T00:00:00.000Z","score":0.00576,"percentile":null},{"date":"2026-10-13T00:00:00.000Z","score":0.00576,"percentile":null},{"date":"2026-10-14T00:00:00.000Z","score":0.00576,"percentile":null},{"date":"2026-10-15T00:00:00.000Z","score":0.00576,"percentile":null},{"date":"2026-10-16T00:00:00.000Z","score":0.00576,"percentile":null},{"date":"2026-10-17T00:00:00.000Z","score":0.00576,"percentile":null},{"date":"2026-10-18T00:00:00.000Z","score":0.00576,"percentile":null},{"date":"2026-10-19T00:00:00.000Z","score":0.00576,"percentile":null},{"date":"2026-10-20T00:00:00.000Z","score":0.00576,"percentile":0.46474}]},"kev":{"state":"not-listed","entries":[],"listedCount":0,"totalCatalogs":3,"catalogs":[{"source":"cisa","label":"CISA","listed":false,"entry":null},{"source":"enisa","label":"ENISA","listed":false,"entry":null},{"source":"circl","label":"CIRCL","listed":false,"entry":null}]},"ransomware":{"state":"none-recorded","sources":[]},"exploits":[],"exploitCount":0,"weaknesses":[{"id":"CWE-287","name":"Improper 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