CVE-2021-42839
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 · uneditedGrand Vice info Co. webopac7 file upload function fails to filter special characters. While logging in with general user’s permission, remote attackers can upload malicious script and execute arbitrary code to control the system or interrupt services.
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 webopac7 application contains an authenticated file upload vulnerability where the upload function fails to properly filter special characters in uploaded files. An attacker with standard user credentials can upload malicious script files and achieve arbitrary code execution on the server.
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= 1.8.20160701= 7.1.20160701CVSS 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
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:L/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 Vice Webopac is installedSearch the system for webopac7 application files, typically found in web server document roots or application directories. Look for directories named 'webopac' or 'webopac7'.Affected if Vice Webopac application files are present on the system
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Determine installed webopac versionLocate version information in the application installation directory, configuration files, or the application's login/about page. Compare against the affected versions 1.8.20160701 and 7.1.20160701.Affected if Installed version matches or falls within the affected version range
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Verify upload functionality is enabledCheck if the file upload feature is accessible to authenticated standard users. Log in with standard user credentials and attempt to access the upload or file attachment section of the webopac web interface.Affected if Upload feature is enabled and accessible to standard (non-admin) users
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Inspect upload directory configurationLocate the configured upload directory in webopac configuration files. Check if uploaded files are stored within the web server's document root.Affected if Upload directory is within the web root and allows script execution
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Check file permission settings on upload directoriesExamine the file system permissions on the upload directory. Verify whether the web server has execute permissions that could allow uploaded scripts to run.Affected if Upload directory permits script execution or lacks proper permission restrictions
A system is affected if Vice Webopac versions 1.8.20160701 or 7.1.20160701 are installed with the upload feature accessible to standard users and the upload directory allows script execution.
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.
From vendor dataImplement strict allowlist-based file type validation, sanitize file names by removing special characters, store uploaded files outside the web root directory, and disable script execution permissions on upload directories.
- Consultation3.0 h
- Implementation6.0 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 $3,984.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-42839 — 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-2021-42839 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