CVE-2026-81921 — In Concrete CMS 8.5.3 to 9,5,2, OAuth 2.0 Refresh-Token Grant Bypasses Account Status

Description (CNA)

Concrete CMS 8.5.3 through 9.5.2 enabled the OAuth 2.0 refresh-token grant using the unmodified upstream League grant, which issued new access tokens from a valid refresh token without re-checking the associated account's active status. A user who obtained a refresh token while active could therefore continue to mint valid access tokens after being deactivated or suspended (uIsActive=0), so deactivating an account did not revoke its API access. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 2.3 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:L/VI:L/VA:L/SC:L/SI:L/SA:L. Thanks sh4d0byss for reporting.

Affected (CNA)

Vendor / product	Versions
Concrete CMS / Concrete CMS	affected 8.5.3 through 9.5.2

CWE

CWE-862

References

https://documentation.concretecms.org/developers/introduction/version-history/953-release-notes

ADP enrichment

CISA-ADP

No English description supplied.

No references supplied.