CVE-2021-40966
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 · uneditedA Stored XSS exists in TinyFileManager All version up to and including 2.4.6 in /tinyfilemanager.php when the server is given a file that contains HTML and javascript in its name. A malicious user can upload a file with a malicious filename containing javascript code and it will run on any user browser when they access the server.
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 confidenceTinyFileManager up to v2.4.6 suffers from a stored XSS vulnerability where malicious HTML/JavaScript can be embedded in uploaded filenames. When other users browse the file manager and access files with malicious filenames, the embedded script executes in their browsers.
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<= 2.4.6CVSS 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
- Required
- Scope
- Changed
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/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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Check the TinyFileManager versionLocate the source file (typically source.php or class.php) and search for a version variable or string. Common locations include the header comments or a $version variable. Compare the found version to 2.4.6.Affected if The installed version is 2.4.6 or lower.
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Verify if file upload functionality is enabledCheck the configuration file (config.php or config.php.default) for settings that enable upload capability. Look for parameters like $allow_upload or similar configuration that controls whether users can upload files.Affected if File uploads are enabled in the configuration.
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Inspect uploaded filenames for malicious contentNavigate to the directory where uploaded files are stored (configured via $upload_dir or similar). List all files and examine filenames for HTML tags, script elements, or JavaScript event handlers (such as <script>, <img onerror=, <svg onload=, javascript:, etc.).Affected if Any uploaded files have filenames containing HTML or JavaScript code.
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Test file listing for XSS executionAccess the TinyFileManager web interface and browse to a directory with uploaded files. View the page source or inspect elements to see if filenames are rendered with proper encoding or if raw HTML/JavaScript is present in the DOM.Affected if Filenames are displayed without proper HTML encoding/sanitization in the file listing.
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Check if the application performs filename sanitizationExamine the source code responsible for handling file uploads and displaying filenames. Look for sanitization functions (such as htmlspecialchars, strip_tags, or similar) applied to filenames before output.Affected if No sanitization functions are applied to filenames before rendering them in the UI.
A user is affected if they are running TinyFileManager version 2.4.6 or lower with uploads enabled, and malicious filenames exist in the system or can be uploaded without sanitization.
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 · scopedImplement strict input validation to sanitize filenames during upload and apply proper output encoding when rendering filenames in the UI to prevent XSS execution.
Tiny File Manager 2.4.7 or later
- 1. Navigate to the Tiny File Manager GitHub repository (github.com/prasathmani/tinyfilemanager)
- 2. Download the latest stable release version (2.4.7 or later)
- 3. Back up your current tinyfilemanager.php configuration and any custom settings
- 4. Replace the existing tinyfilemanager.php with the new version
- 5. Restore your configuration settings to the new installation
- 6. Verify the application functions 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 / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,800.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-40966 — 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-2021-40966 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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