{"id":"CVE-2026-81921","state":"PUBLISHED","title":"In Concrete CMS 8.5.3 to 9,5,2, OAuth 2.0 Refresh-Token Grant Bypasses Account Status","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.","publishedAt":"2026-09-15T18:48:52.840Z","updatedAt":"2026-09-15T19:28:31.335Z","severity":{"score":2.3,"label":"Low","version":"4.0","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","source":"ConcreteCMS"},"assigner":"ConcreteCMS","products":["Concrete CMS Concrete CMS"],"affected":[{"vendor":"Concrete CMS","product":"Concrete CMS","defaultStatus":"unaffected","versions":[{"version":"8.5.3","status":"affected","lessThanOrEqual":"9.5.2","versionType":"git"}],"collectionURL":"https://github.com/concretecms/concretecms","repo":"https://github.com/concretecms/concretecms"}],"references":["https://documentation.concretecms.org/developers/introduction/version-history/953-release-notes"],"weaknesses":["CWE-862"],"ingestedAt":"2026-10-29T20:13:15.269Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/81xxx/CVE-2026-81921.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-81921","state":"PUBLISHED","datePublished":"2026-09-15T18:48:52.840Z","dateUpdated":"2026-09-15T19:28:31.335Z","assignerShortName":"ConcreteCMS","assignerOrgId":"ff5b8ace-8b95-4078-9743-eac1ca5451de","dateReserved":"2026-08-27T18:23:01.366Z"},"containers":{"cna":{"title":"In Concrete CMS 8.5.3 to 9,5,2, OAuth 2.0 Refresh-Token Grant Bypasses Account Status","descriptions":[{"lang":"en","value":"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":[{"vendor":"Concrete CMS","product":"Concrete CMS","defaultStatus":"unaffected","versions":[{"version":"8.5.3","status":"affected","lessThanOrEqual":"9.5.2","versionType":"git"}],"collectionURL":"https://github.com/concretecms/concretecms","repo":"https://github.com/concretecms/concretecms"}],"references":[{"url":"https://documentation.concretecms.org/developers/introduction/version-history/953-release-notes","tags":["release-notes"]}],"metrics":[{"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}],"cvssV4_0":{"attackVector":"NETWORK","attackComplexity":"LOW","attackRequirements":"PRESENT","privilegesRequired":"LOW","userInteraction":"NONE","vulnConfidentialityImpact":"LOW","subConfidentialityImpact":"LOW","vulnIntegrityImpact":"LOW","subIntegrityImpact":"LOW","vulnAvailabilityImpact":"LOW","subAvailabilityImpact":"LOW","exploitMaturity":"NOT_DEFINED","Safety":"NOT_DEFINED","Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","valueDensity":"NOT_DEFINED","vulnerabilityResponseEffort":"NOT_DEFINED","providerUrgency":"NOT_DEFINED","version":"4.0","baseSeverity":"LOW","baseScore":2.3,"vectorString":"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"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-862","lang":"en","description":"CWE-862 Missing Authorization","type":"CWE"}]}],"providerMetadata":{"shortName":"ConcreteCMS","orgId":"ff5b8ace-8b95-4078-9743-eac1ca5451de","dateUpdated":"2026-09-15T18:48:52.840Z"},"impacts":[{"capecId":"CAPEC-1","descriptions":[{"lang":"en","value":"CAPEC-1 Accessing Functionality Not Properly Constrained by ACLs"}]}],"credits":[{"lang":"en","value":"sh4d0byss","type":"finder"}],"source":{"defect":["HackerOne"],"advisory":"3873364","discovery":"EXTERNAL"},"x_generator":{"engine":"Vulnogram 1.0.5"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-09-15T19:28:23.386520Z","id":"CVE-2026-81921","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-09-15T19:28:31.335Z"}}]}}}