The Ultimate Multisite WordPress plugin before 2.17.0 does not require authentication before a logged-out checkout is linked to, and logged in as, an existing WordPress account matching the submitted email address, and its duplicate-account check normalizes that address differently from the lookup used to create the customer, so an unauthenticated attacker can log in as any existing user, including a Network Super Admin, whose email address they know. This bypass is not addressed by the 2.15.1 fix for CVE-2026-75957 and remains exploitable in all versions up to and including 2.16.1, the releases that fix was expected to cover. Exploitation requires a checkout form configured without a password field (auto-generated password) and a target account that has no existing customer record in the Ultimate Multisite WordPress plugin before 2.17.0.
History

Fri, 09 Oct 2026 09:15:00 +0000

Type Values Removed Values Added
First Time appeared Wordpress-extensions
Wordpress-extensions ultimate Multisite
Vendors & Products Wordpress-extensions
Wordpress-extensions ultimate Multisite

Thu, 08 Oct 2026 11:30:00 +0000

Type Values Removed Values Added
Metrics cvssV3_1

{'score': 9.8, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'}

ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}


Thu, 08 Oct 2026 08:00:00 +0000

Type Values Removed Values Added
Weaknesses CWE-287

Thu, 08 Oct 2026 06:15:00 +0000

Type Values Removed Values Added
Description The Ultimate Multisite WordPress plugin before 2.17.0 does not require authentication before a logged-out checkout is linked to, and logged in as, an existing WordPress account matching the submitted email address, and its duplicate-account check normalizes that address differently from the lookup used to create the customer, so an unauthenticated attacker can log in as any existing user, including a Network Super Admin, whose email address they know. This bypass is not addressed by the 2.15.1 fix for CVE-2026-75957 and remains exploitable in all versions up to and including 2.16.1, the releases that fix was expected to cover. Exploitation requires a checkout form configured without a password field (auto-generated password) and a target account that has no existing customer record in the Ultimate Multisite WordPress plugin before 2.17.0.
Title Ultimate Multisite < 2.17.0 - Unauthenticated Authentication Bypass via 'email_address' Parameter
References

cve-icon MITRE

Status: PUBLISHED

Assigner: WPScan

Published: 2026-10-08T06:00:05.353Z

Updated: 2026-10-08T10:59:19.784Z

Reserved: 2026-10-01T06:42:15.491Z

Link: CVE-2026-103646

cve-icon Vulnrichment

Updated: 2026-10-08T10:57:01.628Z

cve-icon NVD

Status : Deferred

Published: 2026-10-08T06:16:37.957

Modified: 2026-10-08T20:51:18.123

Link: CVE-2026-103646

cve-icon Redhat

No data.