CVE-2021-40097
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 · uneditedAn issue was discovered in Concrete CMS through 8.5.5. Authenticated path traversal leads to to remote code execution via uploaded PHP code, related to the bFilename parameter.
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 versions through 8.5.5 contain an authenticated path traversal vulnerability in the file upload functionality. The bFilename parameter is not properly sanitized, allowing an authenticated attacker to traverse directories and upload malicious PHP files, leading to remote code execution.
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<= 8.5.5CVSS 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
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/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 Concrete CMS versionLog into the dashboard and navigate to Dashboard > System & Settings > About Concrete CMS, or check the version file in /config/app.php if accessible via file systemAffected if The installed version is 8.5.5 or earlier (any version through 8.5.5)
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Verify authenticated user file upload accessNavigate to Dashboard > Files > File Manager as an authenticated user and attempt to access or use the file upload functionalityAffected if Authenticated users have access to the file upload feature without additional restrictions
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Inspect upload request parametersIf you have access to application logs or can perform a test upload, examine the HTTP request for the bFilename parameter in the file upload form/processAffected if The bFilename parameter accepts path traversal sequences (such as ../) without sanitization or rejection
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Scan for unauthorized PHP files in web directoriesSearch the /files/ or /application/files/ directory (or custom upload directories) for .php files that were not intentionally uploaded through the proper CMS workflowAffected if Unexpected PHP files exist in upload directories, indicating possible exploitation
You are affected if your Concrete CMS installation is version 8.5.5 or earlier and authenticated users can access the file upload functionality without the bFilename parameter being validated.
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 · scopedUpgrade Concrete CMS to version 8.5.6 or later. If immediate patching is not possible, implement strict input validation on the bFilename parameter and restrict file upload permissions for authenticated users.
Concrete CMS 8.5.6 or later
- 1. Back up your Concrete CMS database and files before making any changes
- 2. Download Concrete CMS version 8.5.6 or later from the official Concrete CMS repository or website
- 3. Replace the core CMS files with the new version, preserving your configuration and site files
- 4. Run any available database migrations if required by the new version
- 5. Verify the installation by logging in and testing file upload functionality
- 6. Confirm the bFilename parameter is now properly sanitized and path traversal is prevented
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation3.0 h
- Implementation6.0 h
- Testing4.0 h
- Review / QA3.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,512.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-40097 — 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-2021-40097 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
- No spam, self-promotion, credentials, or personal data