{"id":"CVE-2026-81905","state":"PUBLISHED","title":"Concrete CMS below 9.5.3 does not enforce validation-hash type on redemption, allowing a hash issued for one purpose to be redeemed for another.","description":"Concrete CMS below 9.5.3 stores user validation hashes for multiple purposes (email/registration validation, password reset, and persistent login) in a single table with a type column, but the redemption path resolves a hash by value alone and does not verify its type. As a result, a hash issued for one purpose can be redeemed for another: a long-lived registration hash (60-day expiry) can be submitted to the password-change endpoint to set a new password on the target account, and a password-reset hash can be submitted to the email-validation endpoint to activate an account. Exploitation requires the attacker to first obtain a valid hash through a separate channel (for example email interception, log exposure, or SSRF against an internal mail relay), so the flaw amplifies the impact of any hash disclosure rather than creating a standalone entry point. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 6.3 with vector CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N. Thanks Yonatan Drori from Tenzai for reporting.","publishedAt":"2026-09-10T23:16:31.052Z","updatedAt":"2026-09-11T14:31:47.993Z","severity":{"score":6.3,"label":"Medium","version":"4.0","vector":"CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N","source":"ConcreteCMS"},"assigner":"ConcreteCMS","products":["Concrete CMS Concrete CMS"],"affected":[{"vendor":"Concrete CMS","product":"Concrete CMS","defaultStatus":"unaffected","versions":[{"version":"5.0.0","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-863","CWE-640"],"ingestedAt":"2026-10-29T20:13:15.269Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/81xxx/CVE-2026-81905.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-81905","state":"PUBLISHED","datePublished":"2026-09-10T23:16:31.052Z","dateUpdated":"2026-09-11T14:31:47.993Z","assignerShortName":"ConcreteCMS","assignerOrgId":"ff5b8ace-8b95-4078-9743-eac1ca5451de","dateReserved":"2026-08-27T18:21:25.200Z"},"containers":{"cna":{"title":"Concrete CMS below 9.5.3 does not enforce validation-hash type on redemption, allowing a hash issued for one purpose to be redeemed for another.","descriptions":[{"lang":"en","value":"Concrete CMS below 9.5.3 stores user validation hashes for multiple purposes (email/registration validation, password reset, and persistent login) in a single table with a type column, but the redemption path resolves a hash by value alone and does not verify its type. As a result, a hash issued for one purpose can be redeemed for another: a long-lived registration hash (60-day expiry) can be submitted to the password-change endpoint to set a new password on the target account, and a password-reset hash can be submitted to the email-validation endpoint to activate an account. Exploitation requires the attacker to first obtain a valid hash through a separate channel (for example email interception, log exposure, or SSRF against an internal mail relay), so the flaw amplifies the impact of any hash disclosure rather than creating a standalone entry point. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 6.3 with vector CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N. Thanks Yonatan Drori from Tenzai for reporting."}],"affected":[{"vendor":"Concrete CMS","product":"Concrete CMS","defaultStatus":"unaffected","versions":[{"version":"5.0.0","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":"HIGH","attackRequirements":"PRESENT","privilegesRequired":"NONE","userInteraction":"NONE","vulnConfidentialityImpact":"LOW","subConfidentialityImpact":"NONE","vulnIntegrityImpact":"LOW","subIntegrityImpact":"NONE","vulnAvailabilityImpact":"NONE","subAvailabilityImpact":"NONE","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":"MEDIUM","baseScore":6.3,"vectorString":"CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-863","lang":"en","description":"CWE-863 Incorrect Authorization","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-640","lang":"en","description":"CWE-640 Weak Password Recovery Mechanism for Forgotten Password","type":"CWE"}]}],"providerMetadata":{"shortName":"ConcreteCMS","orgId":"ff5b8ace-8b95-4078-9743-eac1ca5451de","dateUpdated":"2026-09-10T23:16:31.052Z"},"impacts":[{"capecId":"CAPEC-21","descriptions":[{"lang":"en","value":"CAPEC-21 Exploitation of Trusted Identifiers"}]}],"credits":[{"lang":"en","value":"tenzai","type":"finder"}],"source":{"defect":["HackerOne"],"advisory":"3803371","discovery":"EXTERNAL"},"x_generator":{"engine":"Vulnogram 1.0.5"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-09-11T14:28:56.366688Z","id":"CVE-2026-81905","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":"2026-09-11T14:31:47.993Z"}}]}}}