CVE-2021-26642
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 · uneditedWhen uploading an image file to a bulletin board developed with XpressEngine, a vulnerability in which an arbitrary file can be uploaded due to insufficient verification of the file. A remote attacker can use this vulnerability to execute arbitrary code on the server where the bulletin board is running.
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 an arbitrary file upload vulnerability in XpressEngine bulletin board software. The application fails to properly validate uploaded image files, allowing attackers to bypass file type checks and upload malicious files (such as PHP shells) that can be executed by the web server to achieve 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< 3.0.14CVSS 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 XpressEngine installation and versionLocate the XpressEngine installation directory and find the version file or check the admin panel for the installed version numberAffected if The installed version is XpressEngine and is below 3.0.14
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Verify file upload functionality is enabledCheck if the bulletin board file upload module or plugin is installed and active in the XpressEngine admin panel or configuration filesAffected if File upload feature is enabled on the bulletin board
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Inspect uploaded file storage locationExamine the web server configuration and XpressEngine settings to determine where uploaded files are stored relative to the web rootAffected if Uploaded files are stored in a directory accessible via web browser without restrictions
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Check file type validation configurationReview XpressEngine upload handler configuration or code to see if MIME type, extension, and content validation are implementedAffected if File upload validation relies solely on client-side checks or missing server-side validation for image file types
The environment is affected if XpressEngine version is below 3.0.14 AND the bulletin board file upload feature is enabled, allowing unauthenticated users to upload files to a web-accessible directory.
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 · scoped3.0.14
Implement strict server-side file validation (MIME type, magic bytes, and extension), store uploads outside the web root, disable script execution in upload directories, and/or upgrade to a patched version of XpressEngine.
XpressEngine 3.0.14 or later
- Upgrade XpressEngine to version 3.0.14 or later to address the unrestricted file upload vulnerability
- After upgrading, verify that file upload functionality works correctly and that arbitrary file types are properly blocked
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation8.0 h
- Testing4.0 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 $5,696.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-26642 — 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-2021-26642 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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