CVE-2026-8428
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedConcrete 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceConcrete CMS 9.5.0 and below has a CSRF vulnerability in the dashboard system update functionality. The do_update() method renders a CSRF token in the form via $token->output('do_update'), but the corresponding server-side handler never validates this token with $this->token->validate('do_update'). This allows attackers to craft cross-site POST requests that trigger core CMS updates to attacker-specified version strings, provided the victim passes canUpgrade() and a valid update exists in DIR_CORE_UPDATES.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data< 9.5.1CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- Required
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Check installed Concrete CMS versionLocate the version file in your Concrete CMS installation (typically version.txt or in the application/config directory) and compare it to the affected range: versions below 9.5.1 are vulnerableAffected if installed version is 9.5.0 or below
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Locate the vulnerable update controller fileVerify the file concrete/controllers/single_page/dashboard/system/update/update.php exists in your installationAffected if the file exists and you are running a version below 9.5.1
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Inspect the do_update() method for CSRF validationOpen the update.php controller file and examine the do_update() method. Look for a call to validate the CSRF token (search for 'token->validate' or similar validation logic) before processing the update requestAffected if the do_update() method does NOT contain a token validation call before processing update parameters
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Confirm administrative access to dashboard update featureVerify that the affected user account has access to the Dashboard > System > Update functionality. This is typically restricted to administrators onlyAffected if you have an authenticated administrator session able to access the system update page
You are affected if running Concrete CMS version below 9.5.1 and the do_update() method in the dashboard update controller lacks CSRF token validation before processing update requests.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped9.5.1
Add CSRF token validation ($this->token->validate('do_update')) at the beginning of the do_update() method in concrete/controllers/single_page/dashboard/system/update/update.php to reject unauthenticated update requests.
Concrete CMS 9.5.1
- 1. Back up your Concrete CMS database and all files before performing any upgrade.
- 2. Download Concrete CMS version 9.5.1 or later from the official source at concretecms.com or via your package manager.
- 3. Follow the standard Concrete CMS upgrade procedure: replace core files while preserving the /application/config/ directory and any custom themes or packages.
- 4. Run the upgrade process by accessing your site - the CMS will automatically apply database migrations.
- 5. Verify the installation is running version 9.5.1 or later by checking the dashboard or viewing the version file.
- 6. Test that the dashboard update functionality works correctly after the upgrade.
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation3.0 h
- Implementation2.0 h
- Testing3.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-8428 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-8428 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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