{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-8421", "assignerOrgId": "ff5b8ace-8b95-4078-9743-eac1ca5451de", "state": "PUBLISHED", "assignerShortName": "ConcreteCMS", "dateReserved": "2026-05-12T17:45:47.269Z", "datePublished": "2026-05-21T20:25:11.868Z", "dateUpdated": "2026-05-22T13:23:17.770Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "ff5b8ace-8b95-4078-9743-eac1ca5451de", "shortName": "ConcreteCMS", "dateUpdated": "2026-05-21T20:25:11.868Z"}, "title": "Concrete CMS 9.5.0 and below is vulnerable to CSRF on install_package() with conditional token bypass leading to RCE", "problemTypes": [{"descriptions": [{"lang": "en", "cweId": "CWE-352", "description": "CWE-352 Cross-Site request forgery (CSRF)", "type": "CWE"}]}], "impacts": [{"capecId": "CAPEC-193", "descriptions": [{"lang": "en", "value": "CAPEC-193 PHP Remote File Inclusion"}]}], "affected": [{"vendor": "Concrete CMS", "product": "Concrete CMS", "collectionURL": "https://github.com/concretecms/concretecms", "repo": "https://github.com/concretecms/concretecms", "versions": [{"status": "affected", "version": "5.0", "lessThanOrEqual": "9.5.0", "versionType": "git"}], "defaultStatus": "unaffected"}], "descriptions": [{"lang": "en", "value": "Concrete CMS 9.5.0 and below contains a CSRF vulnerability in the install_package() method of concrete/controllers/single_page/dashboard/extend/install.php. \u00a0An attacker who can cause an authenticated administrator to visit a crafted page,\u00a0 and who has placed or caused a package to be present under DIR_PACKAGES/<handle>/, can force the installation of that package without any CSRF protection. Package installation executes the package controller's install() method as the web server user, enabling remote code execution.\u00a0\u00a0In order to be vulnerable, the victim must be passing canInstallPackages.\u00a0The Concrete CMS security team gave this vulnerability a CVSS v.4.0 score of\u00a07.5 with vector\u00a0CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N. Thanks\u00a0 https://github.com/maru1009 \u00a0for reporting.", "supportingMedia": [{"type": "text/html", "base64": false, "value": "Concrete CMS 9.5.0 and below contains a CSRF vulnerability in the <code>install_package()</code> method of <code>concrete/controllers/single_page/dashboard/extend/install.php</code>. &nbsp;An attacker who can cause an authenticated administrator to visit a crafted page,&nbsp; and who has placed or caused a package to be present under <code>DIR_PACKAGES/&lt;handle&gt;/</code>, can force the installation of that package without any CSRF protection. Package installation executes the package controller's <code>install()</code> method as the web server user, enabling remote code execution.&nbsp;&nbsp;In order to be vulnerable, the victim must be passing <code>canInstallPackages</code>.&nbsp;The Concrete CMS security team gave this vulnerability a CVSS v.4.0 score of&nbsp;7.5 with vector&nbsp;CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N. Thanks&nbsp;<a target=\"_blank\" href=\"https://github.com/maru1009\">https://github.com/maru1009</a>&nbsp;for reporting.<br>"}]}], "references": [{"url": "https://documentation.concretecms.org/9-x/developers/introduction/version-history/951-release-notes", "tags": ["release-notes"]}], "metrics": [{"format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}], "cvssV4_0": {"attackVector": "NETWORK", "attackComplexity": "HIGH", "attackRequirements": "PRESENT", "privilegesRequired": "NONE", "userInteraction": "ACTIVE", "vulnConfidentialityImpact": "HIGH", "subConfidentialityImpact": "NONE", "vulnIntegrityImpact": "HIGH", "subIntegrityImpact": "NONE", "vulnAvailabilityImpact": "HIGH", "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": "HIGH", "baseScore": 7.5, "vectorString": "CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N"}}], "source": {"discovery": "UNKNOWN"}, "x_generator": {"engine": "Vulnogram 1.0.2"}}, "adp": [{"metrics": [{"other": {"type": "ssvc", "content": {"timestamp": "2026-05-22T13:23:11.489309Z", "id": "CVE-2026-8421", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "total"}], "role": "CISA Coordinator", "version": "2.0.3"}}}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-05-22T13:23:17.770Z"}}]}}

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