CVE-2020-8821
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 · uneditedAn Improper Data Validation Vulnerability exists in Webmin 1.941 and earlier affecting the Command Shell Endpoint. A user may enter HTML code into the Command field and submit it. Then, after visiting the Action Logs Menu and displaying logs, the HTML code will be rendered (however, JavaScript is not executed). Changes are kept across users.
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 confidenceWebmin versions 1.941 and earlier contain an improper data validation vulnerability in the Command Shell feature. Attackers can inject arbitrary HTML into the Command field, which gets stored and rendered when users view the Action Logs page. Although JavaScript execution is blocked (preventing full XSS), the HTML injection still allows for defacement, phishing via fake content injection, and potential information disclosure through visual manipulation. The malicious payload persists across user sessions.
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<= 1.941CVSS 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 Webmin versionAccess the Webmin dashboard and navigate to the version information page, or check the package manager for the installed webmin package versionAffected if The installed version is 1.941 or any earlier version
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Verify Command Shell module statusCheck if the Command Shell feature is enabled in Webmin configuration under the available modules or plugins sectionAffected if The Command Shell module is present and enabled in the Webmin installation
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Confirm Action Logs functionality existsNavigate to the Action Logs page within Webmin to verify this feature is accessible (typically under the Webmin or System logs section)Affected if The Action Logs page is accessible to users
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Inspect stored Command entriesReview the Command Shell history or logs to see if any entries contain unescaped HTML tags (look for <script>, <iframe>, <div>, or other HTML elements in stored commands)Affected if Stored Command Shell entries contain raw HTML tags without proper entity encoding
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Check for unauthorized or suspicious Command entriesExamine the Command history for unexpected commands containing HTML payloads or defacement contentAffected if There are Command entries with injected HTML content or unexpected visual elements in the logs
A user is affected if they are running Webmin version 1.941 or earlier with the Command Shell module enabled and the Action Logs page is accessible, as this allows stored HTML injection to be rendered.
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 proper input validation and output encoding in the Command Shell endpoint and Action Logs display. HTML entities should be escaped before storage or rendering. Consider implementing a content security policy as defense-in-depth.
- Consultation2.0 h
- Implementation4.0 h
- Testing2.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-8821 — 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-2020-8821 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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- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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