CVE-2021-26628
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 · uneditedInsufficient script validation of the admin page enables XSS, which causes unauthorized users to steal admin privileges. When uploading file in a specific menu, the verification of the files is insufficient. It allows remote attackers to upload arbitrary files disguising them as image files.
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 confidenceThis is a cross-site scripting (XSS) vulnerability in an admin page's file upload functionality. The application insufficiently validates uploaded files, allowing attackers to disguise arbitrary files (potentially malicious scripts) as image files. Combined with the XSS issue, this can enable unauthorized users to steal admin privileges.
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< 1.9.6.1CVSS 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
- Changed
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/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 Maxb Maxboard installationLocate the Maxb Maxboard application and determine its installed version by checking version files, admin dashboards, or application metadataAffected if The installed version is below 1.9.6.1
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Locate admin page file upload functionalityAccess the admin interface and navigate to any file upload features, particularly those for uploading images or attachmentsAffected if File upload functionality exists in the admin panel
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Verify lack of content-type validationInspect the file upload handler code or intercept upload requests to check if the application validates file content/magic bytes rather than just file extensionsAffected if The application only checks file extensions without validating actual file content
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Test for XSS in upload processUpload a file with a malicious filename containing script tags or upload a file with embedded scripts disguised as an image, then check if the filename is reflected without proper encoding in the admin interfaceAffected if Uploaded filenames are displayed in the admin interface without sanitization or encoding
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Check for admin privilege exposureAfter uploading a malicious file, attempt to access the uploaded file through the admin interface and observe if session tokens, admin credentials, or privileged actions can be interceptedAffected if The XSS combined with file upload allows stealing admin session data or privileges
A user is affected if they are running Maxb Maxboard version below 1.9.6.1 and have the admin file upload feature accessible, which does not properly validate file content and reflects upload metadata without encoding
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 · scoped1.9.6.1
Implement strict server-side file type validation (not just extension checking), validate file content/magic bytes, sanitize file metadata, and add proper output encoding for any reflected content in the admin interface.
Maxboard 1.9.6.1 or later
- 1. Backup the current Maxboard installation and database
- 2. Download Maxboard version 1.9.6.1 or later from the official source
- 3. Extract the new version files
- 4. Replace the existing application files with the new version files
- 5. Verify the upgrade was successful by logging into the admin panel
- 6. Test the file upload functionality to confirm the XSS vulnerability is remediated
- 7. Ensure file upload validation now properly checks file content and rejects malicious files
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation8.0 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 $6,176.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-26628 — 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-2021-26628 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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