{"id":"CVE-2026-81921","title":"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","summary":"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. …","severity":"medium","cvss":5.4,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N","cwe":["CWE-862"],"vendor":"concretecms","product":"concrete_cms","affected":["concrete_cms >= 8.5.3, < 9.5.3"],"patched":["concrete_cms 9.5.3"],"published":"2026-09-15","updated":"2026-09-18","sourceUpdated":"2026-09-18T15:29:38.830","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-81921","references":[{"url":"https://documentation.concretecms.org/developers/introduction/version-history/953-release-notes","label":"ff5b8ace-8b95-4078-9743-eac1ca5451de"}],"tags":["nvd","cve.org","score-dispute"],"epss":0.00238,"epssPercentile":0.13364,"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"partial","timestamp":"2026-09-15T19:28:23.386520Z"},"scores":{"nvd":5.4,"cna":2.3},"ingestedAt":"2026-09-15T19:42:58.809Z","slug":"CVE-2026-81921","body":"## Overview\n\nConcrete 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.\n\n## Affected\n\n- `concrete_cms >= 8.5.3, < 9.5.3`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `concrete_cms 9.5.3`","depth":"sunlit","depthScore":30,"depthScoreParts":{"impact":29.7,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[{"seq":206897,"id":"CVE-2026-81921","ts":1789746312316,"field":"cvss","old":"2.3","new":"5.4"},{"seq":206896,"id":"CVE-2026-81921","ts":1789746312316,"field":"severity","old":"low","new":"medium"}]}