Authenticated session access via unchecked OAuth callback
Published Sep 10, 2026 · Updated Sep 10, 2026
Authentication bypass in Concrete CMS 5.0.0 through 9.5.2 allows remote attackers to obtain a session through an existing OAuth binding. The OAuth callback in GenericOauthTypeController accepted the bound UserInfo object and completed login without verifying isActive() or isValidated(). Exploitation requires an existing OAuth binding for a deactivated or email-unvalidated account, after which the callback records the login, dispatches login events, and returns a fully authenticated session.
Summary
What happened
Authentication bypass in Concrete CMS 5.0.0 through 9.5.2 allows remote attackers to obtain a session through an existing OAuth binding. The OAuth callback in GenericOauthTypeController accepted the bound UserInfo object and completed login without verifying isActive() or isValidated(). Exploitation requires an existing OAuth binding for a deactivated or email-unvalidated account, after which the callback records the login, dispatches login events, and returns a fully authenticated session.
The record
- CVE
- CVE-2026-81906
- Published
- Sep 10, 2026
- Updated
- Sep 10, 2026
- Vendor
- Concrete CMS
- Product
- Concrete CMS
- Classifications
- T1078
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Sep 10, 2026CVE publishedPublication date reported by the CVE source.
- Sep 10, 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.
- Affected versionversion=5.0.0 <=9.5.2
What conditions does exploitation require?
What is affected?
Published CVSS scores
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Attacks
What attackers are doing with it
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Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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