# CVE-2026-81921

## Summary

- **CVE ID:** CVE-2026-81921
- **Severity:** LOW
- **CVSS Score:** 2.3 (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)
- **CWE:** CWE-862
- **Published:** Sep 15, 2026
- **Last Modified:** Sep 15, 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.

## Affected Products

- Concrete CMS — Concrete CMS (8.5.3)

## References

- [CNA](https://documentation.concretecms.org/developers/introduction/version-history/953-release-notes)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.21%
- **EPSS Percentile:** 11.0

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-17._