---
id: CVE-2026-81906
title: >-
  Concrete CMS OAuth callback login path prior to version 9.5.3 did not check
  whether an account was active or email-validated before establishing a session
summary: >-
  Concrete CMS OAuth callback login path prior to version 9.5.3 did not check
  whether an account was active or email-validated before establishing a
  session. A deactivated or unvalidated user with an existing OAuth binding
  could complete a…
severity: medium
cvss: 6.3
cvssVector: 'CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N'
cwe:
  - CWE-288
vendor: Concrete CMS
product: Concrete CMS
affected:
  - concrete_cms >= 5.0.0 <= 9.5.2
published: '2026-09-11'
updated: '2026-09-11'
sourceUpdated: '2026-09-11T15:17:06.000'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-81906'
references:
  - url: >-
      https://documentation.concretecms.org/developers/introduction/version-history/953-release-notes
    label: ff5b8ace-8b95-4078-9743-eac1ca5451de
tags:
  - nvd
  - cve.org
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-09-11T14:26:46.492008Z'
cvssSource: cna
epss: 0.00617
epssPercentile: 0.47334
ingestedAt: '2026-09-11T16:45:47.858Z'
---

## Overview

Concrete CMS OAuth callback login path prior to version 9.5.3 did not check whether an account was active or email-validated before establishing a session. A deactivated or unvalidated user with an existing OAuth binding could complete authentication and receive a session that was fully authenticated for the callback response, with the login recorded and login events dispatched. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 6.3 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N. Thanks Yonatan Drori from Tenzai for reporting.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.