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Vulnerability details

CVE-2026-103646

Ultimate Multisite

Ultimate Multisite < 2.17.0 - Unauthenticated Authentication Bypass via 'email_address' Parameter

CVSS 3.1
9.8Critical

Official 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.

CVSS scores

ScoreVersionSourceVector
9.8Critical 3.1 CISA ADP / Vulnrichment (CISA-ADP) CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

VendorProductVersionsSource
— Ultimate Multisite v < 2.17.0 CVEProject cvelistV5 (CNA)

References and advisories

1
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Details

Published
2026-10-08
Last updated
2026-10-08
State
Published
Assigner (CNA)
WPScan

Exploit prediction (EPSS)

0.35%
Probability of exploitation in 30 days
29.6%
Percentile (among all CVEs)

SSVC assessment (CISA)

Automatable
Yes
Exploitation
None
Technical impact
Total

Weaknesses (CWE)

  • CWE-287
    Improper Authentication