Concrete CMS 9.5.0 and below emits a CSRF token in the local_available_update.php view ($token->output('do_update')) but the corresponding do_update() method in concrete/controllers/single_page/dashboard/system/update/update.php never calls $this->token->validate('do_update'). The form is rendered as a POST form, meaning the token reaches the browser, but because the controller discards it without verification, an attacker can craft a cross-site POST that triggers a core CMS update to an attacker-specified version string. In order to be vulnerable, theictim must be passing canUpgrade()anda valid update version must be present under DIR_CORE_UPDATES. The Concrete CMS security team gave this vulnerability a CVSS v.4.0 score of 7.5 with vector CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N. Thanks https://github.com/maru1009 for reporting.
CVE-2026-8428
HIGHNVD 7.57.5—
EchelonGraph scoreMEDIUM confidence
This high-severity CVE scores 7.5 under NVD CVSS v3. EPSS exploit probability: 0.0%, top 95% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).
Triggered by: NVD CVSS baseline
Sources: epss, nvd
7.5
- CVSS v3
- 7.5
- EG Score
- 7.5(medium)
- EPSS
- 5.5%
- KEV
- Not listed
Published
May 21, 2026
Last Modified
May 21, 2026
References (1)
- ff5b8ace-8b95-4078-9743-eac1ca5451dehttps://documentation.concretecms.org/9-x/developers/introduction/version-history/951-release-notes
Frequently asked(5)
What is CVE-2026-8428?
CVE-2026-8428 is a high vulnerability published on May 21, 2026. Concrete CMS 9.5.0 and below emits a CSRF token in the localavailableupdate.php view ($token->output('doupdate')) but the corresponding doupdate() method in concrete/controllers/singlepage/dashboard/system/update/update.php never calls $this->token->validate('doupdate'). The form is rendered as a…
When was CVE-2026-8428 disclosed?
CVE-2026-8428 was first published in the National Vulnerability Database on May 21, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-8428 actively exploited?
CVE-2026-8428 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 5.5% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-8428?
CVE-2026-8428 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2026-8428?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-8428, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.
Dependency Blast Radius
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