{"id":"CVE-2026-18426","title":"Concrete CMS 9.0.0 through 9.5.2 did not enforce a block-level edit-permission check on the Express Form block's control-management actions, which relied solely on CSRF token validation","summary":"Concrete CMS 9.0.0 through 9.5.2 did not enforce a block-level edit-permission check on the Express Form block's control-management actions, which relied solely on CSRF token validation. Because the token is bound to the user and action …","severity":"medium","cvss":6.5,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N","cwe":["CWE-862"],"vendor":"concretecms","product":"concrete_cms","affected":["concrete_cms >= 9.0.0, < 9.5.3"],"patched":["concrete_cms 9.5.3"],"published":"2026-09-15","updated":"2026-09-21","sourceUpdated":"2026-09-21T17:53:06.833","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-18426","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":0.00206,"epssPercentile":0.10935,"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"partial","timestamp":"2026-09-16T17:50:40.687608Z"},"scores":{"nvd":6.5,"cna":2},"ingestedAt":"2026-09-15T20:44:02.615Z","slug":"CVE-2026-18426","body":"## Overview\n\nConcrete CMS 9.0.0 through 9.5.2 did not enforce a block-level edit-permission check on the Express Form block's control-management actions, which relied solely on CSRF token validation. Because the token is bound to the user and action rather than to a specific block, page, or form, an authenticated user with edit access to one Express Form could reuse a validly obtained token to add, modify, or delete controls on Express Forms they were not authorized to edit, including injecting a control whose value is later rendered as HTML to achieve stored XSS. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 2.0 with vector CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:P/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N. Thanks Yat Wu for reporting.\n\n## Affected\n\n- `concrete_cms >= 9.0.0, < 9.5.3`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `concrete_cms 9.5.3`","depth":"sunlit","depthScore":36,"depthScoreParts":{"impact":35.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[{"seq":208691,"id":"CVE-2026-18426","ts":1790016697787,"field":"cvss","old":"2","new":"6.5"},{"seq":208690,"id":"CVE-2026-18426","ts":1790016697787,"field":"severity","old":"low","new":"medium"}]}