CVE-2026-81921
In Concrete CMS 8.5.3 to 9,5,2, OAuth 2.0 Refresh-Token Grant Bypasses Account Status
- State
- Published
- Severity
- 2.3 Low
- Published
- Sep 15, 2026
- Updated
- Sep 15, 2026
- Reserved
- Aug 27, 2026
Description
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 2.3 Low | 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 | ConcreteCMS |
Weaknesses
- CWE-862 Missing Authorization
Affected Products
| Product | Versions |
|---|---|
Concrete CMSConcrete CMS |
|
References
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