CVE-2026-103646
Ultimate Multisite < 2.17.0 - Unauthenticated Authentication Bypass via 'email_address' Parameter
- State
- Published
- Severity
- 9.8 Critical
- Published
- Oct 8, 2026
- Updated
- Oct 8, 2026
- Reserved
- Oct 1, 2026
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 3.1 | 9.8 Critical | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H | CISA-ADP |
Weaknesses
- CWE-287 Improper Authentication
Affected Products
| Product | Versions |
|---|---|
Ultimate MultisiteUnknown |
|
References
- https://wpscan.com/vulnerability/a05da0ad-5d92-406f-b182-b3ed1f8389f3/exploitvdb-entrytechnical-description
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