Ultimate Multisite < 2.17.0 - Unauthenticated Authentication Bypass via 'email_address' Parameter
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.
CVE-2026-103646
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-103646
Ultimate Multisite
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"vendor": "Unknown",
"product": "Ultimate Multisite",
"versions": [
{
"status": "affected",
"version": "0",
"lessThan": "2.17.0",
"versionType": "semver"
}
],
"defaultStatus": "unaffected"
}
]- Related CVEs
- CVE-2026-103646
Source reference:
/cveMetadata/cveId
Publisher severity
No explicit severity was provided.
- Event
- #12423 · Revision 1
- Added to Heist Feed
- Publisher date