CVE-2026-75957Network attack vectorHinoki check available

Unauthenticated account takeover via checkout validation bypass

Published Oct 1, 2026 · Updated Oct 1, 2026

Authentication bypass in David Stone Ultimate Multisite 2.15.0 and earlier lets remote attackers sign in as existing users via checkout. The public checkout AJAX handler accepts an obtainable nonce, skips validation for a crafted checkout_form value, and sets an authentication cookie for the account matching the supplied email address. The target account must lack an Ultimate Multisite customer record; a matching Network Super Admin account grants network-level access.

CVSS severity9.8
Critical
EPSS probability0.58%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Authentication bypass in David Stone Ultimate Multisite 2.15.0 and earlier lets remote attackers sign in as existing users via checkout. The public checkout AJAX handler accepts an obtainable nonce, skips validation for a crafted checkout_form value, and sets an authentication cookie for the account matching the supplied email address. The target account must lack an Ultimate Multisite customer record; a matching Network Super Admin account grants network-level access.

The record

CVE
CVE-2026-75957
Published
Oct 1, 2026
Updated
Oct 1, 2026
Vendor
David Stone
Product
Ultimate Multisite
Classifications
CWE-287, T1078
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 1, 2026CVE publishedPublication date reported by the CVE source.
  2. Oct 1, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <=2.15.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

David Stone · Ultimate Multisiteversion=0 <=2.15.0

Published CVSS scores

9.8Wordfence CNACVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Activity data is delayed. The latest report is Sep 28, 2026.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-287Improper Authentication
T1078Valid Accounts

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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