CVE-2026-81921
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.
Is your site exposed to CVE-2026-81921?
Run a free security scan — no signup, results in seconds.
Weakness Type (CWE)
References
Frequently Asked Questions
What is CVE-2026-81921? +
How do I check if I'm vulnerable to CVE-2026-81921? +
Related Vulnerabilities
FreeScout is a free self-hosted help desk and shared mailbox. Prior to version 1.8.213, the `load_customer_info` action in `POST /conversation/ajax` …
GLPI is a free asset and IT management software package. Starting in version 0.78 and prior to versions 10.0.25 and …
In affected versions of Octopus Server, permissions were not checked correctly resulting in any authenticated user being able to make …
SOPlanning does not enforce authorization for backup functionalities. An unauthenticated attacker can directly query backup-related endpoints and retrieve backup archives …
A denial-of-service vulnerability exists in NPort devices because of improper access control on the command port. The command interface does …
NamelessMC is website software for Minecraft servers. In version 2.2.4,`core/classes/Misc/ProfilePostReactionContext.php` only verifies that the wall post exists and does not …