Ultimate Multisite <= 2.16.0 — Unauthenticated Arbitrary Account Takeover
CVE-2026-103646Published · Updated Action summary
Affected: ≤2.16.0Update to 2.17.0 or newer
All remediation steps- Severity
- High7.3
- CVSS
- 7.3CVSS 3.1 · CNA (Wordfence)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:LWhat does this vector mean?
AV:NAttack vector- Network
AC:LAttack complexity- Low
PR:NPrivileges required- None
UI:NUser interaction- None
S:UScope- Unchanged
C:LConfidentiality- Low
I:LIntegrity- Low
A:LAvailability- Low
- Weakness
- CWE-287 Improper Authentication
- Required access
- No account needed
- Exploit prediction (EPSS)
- 0.4% chance in 30 days29th percentile
- CISA KEV
- Not listed
On this page8
Am I affected?
Ultimate Multisite – WordPress Multisite SaaS & WaaS Platform ultimate-multisite
- Affected≤ 2.16.0
- Patched in2.17.0
Update to 2.17.0 or newer.
You are affected if you run ≤ 2.16.0. Version 2.17.0 and later are not affected by this issue.
- Check your version: in wp-admin go to Plugins → Installed Plugins and read the version under Ultimate Multisite – WordPress Multisite SaaS & WaaS Platform.
- No admin access? Run a passive check of your site. It reads public files only.
- No account is needed to exploit this. Treat any exposed site on an affected version as at risk.
What to do
- Update to version 2.17.0, or a newer patched version
- Rotate administrator passwords and application secrets if the site ran a vulnerable version while publicly reachable.
- Watch Ultimate Multisite – WordPress Multisite SaaS & WaaS Platform to get an email when the next vulnerability is published.
Advisory
Source description from Wordfence Intelligence, credited to Erwan LR.
The Ultimate Multisite plugin for WordPress is vulnerable to Account Takeover in all versions up to, and including, 2.16.0. This is due to missing email normalization before the duplicate-account lookup combined with the absence of a require_new_user guard, allowing a submitted email to be matched to and linked with an existing WordPress user account without authentication. This makes it possible for unauthenticated attackers to log in as any existing WordPress user, including a Network Super Admin, by submitting their known email address through a passwordless checkout form and having the plugin link the unauthenticated checkout session to that existing account. A checkout form must be configured without a password field (auto-generated password mode), and the targeted WordPress account must have no existing customer record in the plugin.
Exploits & references
Proof-of-concept & detection
No public proof-of-concept or detection template is known for this vulnerability.
Advisories & patches
- Advisorywordfence.com
Related CVEs
More in Ultimate Multisite – WordPress Multisite SaaS & WaaS Platform
All 3| Severity | Vulnerability | CVE | Published |
|---|---|---|---|
| High8.1 | Unauthenticated Local File Inclusion <2.17.2Update to 2.17.2 | CVE-2026-107508 | |
| Critical9.8 | Unauthenticated Authentication Bypass via 'checkout_form' Parameter ≤2.15.0Update to 2.15.1 | CVE-2026-75957 |
- High8.1Unauthenticated Local File Inclusion
<2.17.2Update to 2.17.2
- Critical9.8Unauthenticated Authentication Bypass via 'checkout_form' Parameter
≤2.15.0Update to 2.15.1
Timeline
CVE published
Severity high, CVSS 7.3
Record last updated
Sources & licenses
Wordfence record- Vulnerability data
- Wordfence Intelligence. Copyright 2012-2026 Defiant Inc. Licensed under the CC BY-SA 4.0.
- CVE® identifiers
- Copyright 1999-2026 The MITRE Corporation. Used under the CVE Program. CVE® is a registered trademark of The MITRE Corporation.
- CVSS / CWE
- National Vulnerability Database (NVD), shown unmodified. This product uses the NVD API but is not endorsed or certified by the NVD.
- EPSS
- Exploit Prediction Scoring System by FIRST.org.
- VulnCrest content
- Summary, remediation guidance and page layout © VulnCrest. Not sourced from NVD.