Vulnerability Details CVE-2026-81921
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.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.001
EPSS Ranking 3.5%
CVSS Severity
CVSS v3 Score 5.4
References
Products affected by CVE-2026-81921
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cpe:2.3:a:concretecms:concrete_cms:8.5.10
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cpe:2.3:a:concretecms:concrete_cms:8.5.11
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cpe:2.3:a:concretecms:concrete_cms:8.5.12
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cpe:2.3:a:concretecms:concrete_cms:8.5.13
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cpe:2.3:a:concretecms:concrete_cms:8.5.14
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cpe:2.3:a:concretecms:concrete_cms:8.5.15
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cpe:2.3:a:concretecms:concrete_cms:8.5.16
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cpe:2.3:a:concretecms:concrete_cms:8.5.17
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cpe:2.3:a:concretecms:concrete_cms:8.5.18
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cpe:2.3:a:concretecms:concrete_cms:8.5.19
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cpe:2.3:a:concretecms:concrete_cms:8.5.20
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cpe:2.3:a:concretecms:concrete_cms:8.5.21
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cpe:2.3:a:concretecms:concrete_cms:8.5.3
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cpe:2.3:a:concretecms:concrete_cms:8.5.4
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cpe:2.3:a:concretecms:concrete_cms:8.5.5
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cpe:2.3:a:concretecms:concrete_cms:8.5.6
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cpe:2.3:a:concretecms:concrete_cms:8.5.7
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cpe:2.3:a:concretecms:concrete_cms:8.5.8
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cpe:2.3:a:concretecms:concrete_cms:8.5.9
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cpe:2.3:a:concretecms:concrete_cms:9.0
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cpe:2.3:a:concretecms:concrete_cms:9.0.0
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cpe:2.3:a:concretecms:concrete_cms:9.0.1
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cpe:2.3:a:concretecms:concrete_cms:9.0.2
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cpe:2.3:a:concretecms:concrete_cms:9.1.0
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cpe:2.3:a:concretecms:concrete_cms:9.1.1
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cpe:2.3:a:concretecms:concrete_cms:9.1.2
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cpe:2.3:a:concretecms:concrete_cms:9.1.3
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cpe:2.3:a:concretecms:concrete_cms:9.2.0
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cpe:2.3:a:concretecms:concrete_cms:9.2.1
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cpe:2.3:a:concretecms:concrete_cms:9.2.2
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cpe:2.3:a:concretecms:concrete_cms:9.2.3
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cpe:2.3:a:concretecms:concrete_cms:9.2.4
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cpe:2.3:a:concretecms:concrete_cms:9.2.5
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cpe:2.3:a:concretecms:concrete_cms:9.2.6
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cpe:2.3:a:concretecms:concrete_cms:9.2.7
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cpe:2.3:a:concretecms:concrete_cms:9.2.8
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cpe:2.3:a:concretecms:concrete_cms:9.2.9
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cpe:2.3:a:concretecms:concrete_cms:9.3.0
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cpe:2.3:a:concretecms:concrete_cms:9.3.1
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cpe:2.3:a:concretecms:concrete_cms:9.3.2
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cpe:2.3:a:concretecms:concrete_cms:9.3.3
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cpe:2.3:a:concretecms:concrete_cms:9.3.4
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cpe:2.3:a:concretecms:concrete_cms:9.3.5
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cpe:2.3:a:concretecms:concrete_cms:9.3.6
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cpe:2.3:a:concretecms:concrete_cms:9.3.7
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cpe:2.3:a:concretecms:concrete_cms:9.3.8
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cpe:2.3:a:concretecms:concrete_cms:9.3.9
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cpe:2.3:a:concretecms:concrete_cms:9.4.0
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cpe:2.3:a:concretecms:concrete_cms:9.4.1
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cpe:2.3:a:concretecms:concrete_cms:9.4.2
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cpe:2.3:a:concretecms:concrete_cms:9.4.3
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cpe:2.3:a:concretecms:concrete_cms:9.4.4
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cpe:2.3:a:concretecms:concrete_cms:9.4.5
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cpe:2.3:a:concretecms:concrete_cms:9.4.6
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cpe:2.3:a:concretecms:concrete_cms:9.4.7
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cpe:2.3:a:concretecms:concrete_cms:9.4.8
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cpe:2.3:a:concretecms:concrete_cms:9.5.0
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cpe:2.3:a:concretecms:concrete_cms:9.5.1
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cpe:2.3:a:concretecms:concrete_cms:9.5.2