CVE-2026-8427
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 removeFavoriteFolder($id). The Concrete CMS security team gave this vulnerability a CVSS v.4.0 score of 2.3 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N. Thanks Yonatan Drori (Tenzai) for reporting.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceCSRF vulnerability in Concrete CMS 9 before 9.5.0 in the removeFavoriteFolder($id) endpoint of the backend file controller. An attacker can craft a malicious link that, when clicked by an authenticated user, causes the user unknowingly to remove their favorite folder. The CVSS v4.0 vector shows integrity impact (VI:L) but no confidentiality or availability impact.
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>= 9.0.0, < 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
- 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.
-
Identify Concrete CMS versionLocate the version file or check the dashboard footer for the installed Concrete CMS version numberAffected if The installed version is 9.0.0 through 9.5.0 (inclusive)
-
Locate the backend file controllerNavigate to the backend file controller source code that handles the removeFavoriteFolder($id) functionAffected if The controller exists in the codebase and is accessible to authenticated users
-
Inspect removeFavoriteFolder endpoint for CSRF protectionOpen the removeFavoriteFolder function in the file controller and examine whether concrete.secure.key or similar CSRF token validation is performed before processing the requestAffected if The function lacks CSRF token validation logic
-
Verify endpoint accessibilityCheck if the removeFavoriteFolder endpoint can be reached without a valid CSRF token in the request (such as via form submission or AJAX call)Affected if The endpoint processes requests without requiring a valid CSRF token
A user is affected if their Concrete CMS installation is version 9.0.0 through 9.5.0 and the removeFavoriteFolder 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 tokens (synchronizer token pattern) on the removeFavoriteFolder action and ensure all state-changing requests require valid tokens. Upgrade to Concrete CMS 9.5.0 or later if available.
Concrete CMS 9.5.1 or later
- 1. Backup your Concrete CMS database and files before proceeding with any upgrade.
- 2. Download Concrete CMS version 9.5.1 or later from the official Concrete CMS website (documentation.concretecms.org).
- 3. Extract the new version files and replace the existing installation files, preserving your configuration and application-specific files.
- 4. Run the database upgrade process by accessing your site - Concrete CMS will automatically prompt for migration if needed.
- 5. Verify the upgrade was successful by logging into the admin dashboard and checking the version number.
- 6. Test that the file removeFavoriteFolder functionality works correctly after the upgrade.
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-2026-8427 — 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-2026-8427 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
Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.
A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
- 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
- No spam, self-promotion, credentials, or personal data