CVE-2001-0155
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 · uneditedFormat string vulnerability in VShell SSH gateway 1.0.1 and earlier allows remote attackers to execute arbitrary commands via a user name that contains format string specifiers.
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 confidenceFormat string vulnerability in VShell SSH gateway 1.0.1 and earlier allows remote attackers to execute arbitrary commands by supplying format string specifiers (e.g., %s, %x) in the username field. The vulnerability stems from passing user input directly to a format function without proper sanitization, enabling stack manipulation and arbitrary 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<= 1.0.1CVSS 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
- Authentication
- None
- Confidentiality
- Partial
- Integrity
- Partial
- Availability
- Partial
AV:N/AC:L/Au:N/C:P/I:P/A:P
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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Verify VShell SSH service is installedCheck for VShell processes running on the system (e.g., 'vshell.exe' on Windows or look for 'VShell' in running processes via task manager or 'ps aux' on Unix). Also check installed programs list for 'Van Dyke Technologies VShell' or 'VShell SSH Server'.Affected if VShell is found installed on the system
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Determine installed VShell versionLocate the VShell installation directory and check version information in the executable, registry keys (Windows), or version flags (run 'vshell -v' or check the About dialog if available). Compare the version number to the affected range: <= 1.0.1.Affected if The installed version is 1.0.1 or any earlier version (e.g., 1.0.0, 0.9.x)
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Confirm SSH service is listeningVerify the SSH daemon is actively listening on the configured port (default TCP 22) by running 'netstat -an | findstr :22' on Windows or 'netstat -tlnp | grep :22' on Unix, or by scanning the system with an Nmap port scan targeting port 22.Affected if SSH service (VShell) is running and accepting connections on any network interface
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Check if remote authentication is enabledReview VShell configuration files (typically in the VShell install directory or /etc/vshell/ on Unix) to verify the SSH service allows remote user authentication. Look for settings related to password or public key authentication that permit logins from network clients.Affected if Remote authentication is enabled and the SSH service is network-accessible
The system is affected if VShell is installed with version 1.0.1 or earlier and the SSH service is running with remote authentication enabled, as the format string vulnerability can be triggered through the username field during login attempts.
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 dataUpgrade to a patched version of VShell; if no upgrade path exists, implement network-level access controls to restrict SSH access to trusted sources only, as a temporary compensating control.
- Consultation6.0 h
- Implementation8.0 h
- Testing4.0 h
- Review / QA3.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2001-0155 — 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-2001-0155 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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