CVE-2023-6551
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 · uneditedAs a simple library, class.upload.php does not perform an in-depth check on uploaded files, allowing a stored XSS vulnerability when the default configuration is used. Developers must be aware of that fact and use extension whitelisting accompanied by forcing the server to always provide content-type based on the file extension. The README has been updated to include these guidelines.
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 · moderate confidenceclass.upload.php fails to perform adequate validation on uploaded files in its default configuration, allowing attackers to upload files containing malicious JavaScript payloads that execute as stored XSS when users access the uploaded files.
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 dataall versionsCVSS 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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Identify class.upload.php usageSearch your codebase for references to 'class.upload.php' or the Verot upload class (e.g., require/include statements, composer dependencies)Affected if The library is included in the application
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Review upload handling codeLocate the PHP files that handle file uploads and instantiate the upload class. Check for the $handle->allowed array or similar whitelist configurationAffected if No extension whitelist ($allowed) is defined or configured for uploaded files
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Check file type validation logicInspect how uploaded files are validated. Look for MIME type checks, extension checks, or any $handle->allowed() method callsAffected if The code relies on default behavior without explicitly restricting allowed file extensions or MIME types
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Examine upload form configurationReview the HTML forms and server-side handling that process uploads. Identify if client-provided Content-Type headers are trustedAffected if The application accepts uploads without enforcing server-side Content-Type determination based on file extension
If Verot Class.upload.php is in use and extension whitelisting is not explicitly configured, the environment is vulnerable to CVE-2023-6551
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 · scopedConfigure extension whitelisting to permit only safe file types and force the web server to determine Content-Type headers based on file extensions rather than trusting client-provided MIME types.
- Implement extension whitelisting for file uploads - only allow safe extensions (e.g., jpg, png, pdf) and reject all others
- Configure the server to always provide Content-Type headers based on file extension rather than the client-provided MIME type
- Disable execution permissions on the upload directory to prevent uploaded files from being executed as scripts
- Validate uploaded files by checking both the file extension and Content-Type header matches expected values
- Consider using a separate subdomain for user uploads with restrictive headers
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-2023-6551 — 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-2023-6551 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
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