EUVD-2026-75888
GHSA-2c5v-fhhf-mwq5
Severity by source
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
AC:H reflects required precondition of an existing OAuth binding on a deactivated account; no confidentiality impact confirmed by vendor vector.
Primary rating from Vendor (ConcreteCMS).
CVSS VectorVendor: ConcreteCMS
Lifecycle Timeline
2DescriptionCVE.org
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.
AnalysisAI
Concrete CMS versions prior to 9.5.3 allow deactivated or email-unvalidated users to bypass account-status enforcement by authenticating through the OAuth callback path. When a user whose account has been deactivated or whose email address has not been verified holds an existing OAuth provider binding, the CMS completes the OAuth handshake, records a login event, and issues a fully-authenticated session without verifying whether the account is permitted to log in. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires two concurrent preconditions: (1) the target Concrete CMS account must be either deactivated by an administrator or have an unverified email address, AND (2) that same account must have a pre-existing OAuth provider binding established before deactivation or failed validation. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 4.0 vector (AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N, score 6.3) reflects a meaningful constraint via the AT:P (attack requirements present) metric: exploitation demands a pre-existing OAuth binding on the deactivated or unvalidated account, which substantially limits the realistic attacker pool. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Upgrade to Concrete CMS 9.5.3 or later, which introduces account-status and email-validation checks within the OAuth callback handler before a session is issued. … Detailed patch versions, workarounds, and compensating controls in full report. |
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