CVE-2026-8435
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 before 9.5.0 is vulnerable to Cross Site Request Forgery (CSRF) at concrete/controllers/backend/file approveVersion(). The Concrete CMS security team gave this vulnerability a CVSS v.4.0 score of 2.3 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N. Thanks Yonatan Drori (Tenzai) 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 confidenceCross-Site Request Forgery (CSRF) vulnerability in Concrete CMS 9 before 9.5.0 affecting the file version approval endpoint (concrete/controllers/backend/file approveVersion()). An attacker could craft a malicious request that tricks an authenticated administrator into approving a file version without their explicit consent or knowledge.
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>= 9.0, < 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
- None
- Integrity
- High
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
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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Identify Concrete CMS versionCheck the version file in your Concrete CMS installation (typically at /concrete/config/app.php or view the dashboard footer version info)Affected if Version is 9.0.0 through 9.5.0 (before 9.5.1)
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Verify file approval endpoint existsLocate the file approval controller in your installation under concrete/controllers/backend/file.php and check if the approveVersion() method existsAffected if The approveVersion() method exists and is accessible to administrators
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Confirm CSRF token is missing from approval actionOpen the approveVersion() method in the file controller and inspect whether it calls the validateCSRFToken() or similar protection method before processing the approvalAffected if No CSRF token validation is performed before approving file versions
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Check API or form handling for token validationReview the form or API request handling in the file approval workflow to see if any token-based protection is applied at the form or request levelAffected if No anti-CSRF token is required or validated when approving file versions
You are affected if your Concrete CMS version is between 9.0.0 and 9.5.0 inclusive and the file approval endpoint lacks CSRF token validation.
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
Implement anti-CSRF token validation on the approveVersion() endpoint, requiring a valid token for all state-changing requests. Ensure tokens are validated server-side before processing file approval actions.
Concrete CMS 9.5.1 or later
- Back up your Concrete CMS database and all website files before proceeding
- Download Concrete CMS version 9.5.1 (or the latest 9.x release) from the official Concrete CMS website (concretecms.com)
- Upload the new version files to your server, overwriting the existing installation
- Run any database upgrade scripts if prompted during the upgrade process
- Verify the installation by logging into the admin dashboard
- Test that the file approval functionality at concrete/controllers/backend/file works correctly
- Clear any application caches to ensure the new version is fully active
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,088.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-8435 — 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-2026-8435 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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