CVE-2021-44159
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 · unedited4MOSAn GCB Doctor’s file upload function has improper user privilege control. A remote attacker can upload arbitrary files including webshell files without authentication and execute arbitrary code in order to perform arbitrary system operations or deny of service attack.
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 confidenceThe 4MOSAn GCB Doctor application contains a file upload function that lacks both authentication and authorization controls, permitting unauthenticated remote attackers to upload arbitrary files including webshells. This allows execution of arbitrary code on the underlying system.
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< 2021-09-16CVSS 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
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/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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Identify if 4mosan Gcb Doctor is installedSearch for the Gcb Doctor application in your web server directories, typically under /var/www, /home, or C:\inetpub\wwwroot. Look for directories named 'gcb', 'gcbinstall', or similar. Check your installed applications list if this is a hosted service.Affected if The application is found and the installed version predates the 2021-09-16 patch date
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Determine the installed version of Gcb DoctorCheck the application for version information - look in the main executable, DLL files, or any about/info page within the application. Compare the build date or version number to the 2021-09-16 threshold.Affected if The version or build date is earlier than September 16, 2021
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Locate the file upload endpointReview application source code or network traffic to identify the file upload functionality. Common paths include /upload, /fileupload, or endpoints accepting multipart/form-data. Search for form fields named 'file', 'upload', or similar.Affected if The file upload endpoint exists and is accessible without requiring login credentials
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Test if the upload function requires authenticationAttempt to access the file upload endpoint directly via HTTP/HTTPS without providing any session cookie, token, or login credentials. Observe whether the request is accepted or redirected to a login page.Affected if The upload endpoint accepts requests without any authentication token or session cookie, returning a successful response rather than a 401/403 or login redirect
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Inspect the web root for unauthorized uploaded filesSearch the web-accessible directories for suspicious file types: .asp, .php, .jsp, .exe, .bat, .cmd, .sh, or other executable extensions. Check file creation dates that coincide with the time frame of potential exploitation.Affected if Unexpected executable or script files are found in web-accessible directories, particularly with recent creation dates
Your environment is affected if 4mosan Gcb Doctor is installed with a version predating September 16, 2021 AND the file upload endpoint is accessible without authentication.
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 · scoped2021-09-16
Implement mandatory authentication and role-based access control for the file upload function, add strict allowlist-based file type validation, store uploaded files outside the web root, and apply vendor patches if available.
Gcb Doctor version 2021-09-16 or later
- 1. Back up the current Gcb Doctor installation and configuration data before proceeding with the upgrade.
- 2. Obtain the updated Gcb Doctor version released on or after 2021-09-16 from the official vendor (4MOSAn) or authorized distribution channels.
- 3. Install or apply the updated version following the vendor's documented upgrade procedures.
- 4. After installation, verify that the file upload function now properly enforces user authentication and authorization controls.
- 5. Test that arbitrary file uploads are now rejected and that only authorized users can upload files through the proper upload mechanism.
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation12.0 h
- Testing6.0 h
- Review / QA4.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $7,328.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-44159 — 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-2021-44159 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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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