CVE-2021-41738
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 · uneditedZeroShell 3.9.5 has a command injection vulnerability in /cgi-bin/kerbynet IP parameter, which may allow an authenticated attacker to execute system commands.
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 confidenceZeroShell 3.9.5 contains a command injection vulnerability in the /cgi-bin/kerbynet endpoint via the IP parameter. An attacker with valid authentication can inject arbitrary system commands through unsanitized input, potentially leading to full system compromise.
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= 3.9.5CVSS 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 the installed ZeroShell versionAccess the ZeroShell administrative interface or check the system information page to view the running version numberAffected if The installed version is exactly 3.9.5
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Verify the /cgi-bin/kerbynet endpoint existsCheck if the CGI script kerbynet is present in the cgi-bin directory on the web serverAffected if The endpoint exists and is accessible via HTTP/HTTPS
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Confirm authentication is enabled for the vulnerable endpointReview the web server or ZeroShell configuration to verify whether authentication is required to access /cgi-bin/kerbynetAffected if Valid authentication can be obtained (whether default credentials, weak credentials, or a compromised account)
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Check if the IP parameter is processed by kerbynetExamine the kerbynet CGI script or its configuration to determine if it accepts and processes an 'IP' parameter without sanitizationAffected if The IP parameter is accepted and used in system calls without input validation
You are affected if you are running ZeroShell version 3.9.5, the /cgi-bin/kerbynet endpoint is accessible, and an attacker can authenticate to submit unsanitized input to the IP parameter.
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 input validation and sanitization on all user-supplied parameters, particularly the IP parameter in /cgi-bin/kerbynet. Consider applying the latest vendor patch or upgrading to a patched version if available.
- Consultation3.0 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 $3,408.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-41738 — 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-2021-41738 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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