CVE-2026-103646 Ultimate Multisite WordPress - Authentication Bypass

Ultimate Multisite WordPress plugin < 2.17.0 contains an authentication bypass caused by inconsistent email normalization in duplicate-account check, letting unauthenticated attackers log in as existing users, exploit requires checkout form without password and target account without customer record.

CVSS base score 9.8 /10
Critical
CISA KEV
Not listed
Public exploit
None known
Authentication
Not required
EPSS
0.44% chance of exploitation in 30 days
View the NVD record ↗

Details

Type
Authentication Bypass
Impact
Broken Authentication
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Published
8 October 2026
Updated
15 October 2026
Weakness
CWE-287

Vendor fix

Update to version 2.17.0 or later.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

References

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