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Serv U File ServerApplication · Solarwinds

CVE-2009-4006

HIGH · 10.0 CVSS v2.0 Published 2009-11-20
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
100/100
Remediation priority · Urgent
High EPSS Remotely reachable No privileges Zero-click

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 · unedited
Stack-based buffer overflow in the TEA decoding algorithm in RhinoSoft Serv-U FTP server 7.0.0.1, 9.0.0.5, and other versions before 9.1.0.0 allows remote attackers to execute arbitrary code via a long hexadecimal string.

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 confidence

Stack-based buffer overflow in the TEA (Tiny Encryption Algorithm) decoding function in RhinoSoft Serv-U FTP server versions 7.0.0.1 through 9.0.0.x allows remote attackers to execute arbitrary code by sending a specially crafted long hexadecimal string to the FTP service.

MitigationUpgrade Serv-U to version 9.1.0.0 or later which contains the patched TEA decoding implementation. If immediate upgrading is not feasible, restrict network access to the FTP port (typically port 21) to minimize exposure.

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
Serv U File ServerApplication
Affected:= 7.0.0.1= 7.0.0.2= 7.0.0.3= 7.0.0.4= 7.1.0.0= 7.1.0.1= 7.1.0.2= 7.2.0.0= 7.2.0.1= 7.3.0.0= 7.3.0.1= 7.3.0.2

CVSS 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
Complete
Integrity
Complete
Availability
Complete

AV:N/AC:L/Au:N/C:C/I:C/A:C

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 checks

Work through these to decide whether this CVE applies to you.

  1. Confirm Serv-U FTP server is installed
    Check for Serv-U installation by looking for the service: Open Services console (services.msc) and look for 'Serv-U File Server' or 'Serv-U FTP Server' service, or check Program Files for 'Serv-U' folder.
    Affected if Serv-U is not installed on the system.
  2. Identify installed Serv-U version
    If the Serv-U service is present, obtain the version number: Right-click the Serv-U executable (typically in C:\Program Files\Serv-U\ or C:\Program Files (x86)\Serv-U\), select Properties, and view the Version tab. Alternatively, run 'servu.exe -v' from the installation directory if supported.
    Affected if The installed version matches 7.0.0.1 through 7.3.0.2 or falls within 7.x to 9.0.0.x range.
  3. Verify FTP service is listening
    Check if the FTP service port (default 21) is open and listening: Run 'netstat -an | findstr :21' or use PortQry.exe to query port 21 on the local machine.
    Affected if Port 21 is in LISTENING state, indicating the vulnerable service is active and network-accessible.
  4. Confirm TEA decoding is in use
    This vulnerability is in the TEA decoding function triggered by specially crafted hexadecimal strings. The flaw is present by default in affected versions - no specific configuration needs to be enabled for the vulnerability to exist.
    Affected if Serv-U version is within the affected range AND the FTP service is running.

You are affected if Serv-U File Server version 7.0.0.1 through 7.3.0.2 (or any 7.x-9.0.x version) is installed and the FTP service is running and network-accessible.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade Serv-U to version 9.1.0.0 or later which contains the patched TEA decoding implementation. If immediate upgrading is not feasible, restrict network access to the FTP port (typically port 21) to minimize exposure.

Recommended fix High confidence

Serv-U 9.1.0.0 or later

  1. 1. Verify current Serv-U installation version by checking the server administration interface or running 'servu -v' from command line
  2. 2. Download Serv-U version 9.1.0.0 or later from the official SolarWinds (current vendor) download page
  3. 3. Back up current Serv-U configuration files (typically located in the installation directory under 'Config' folder)
  4. 4. Stop the Serv-U FTP service before upgrading
  5. 5. Install the upgraded Serv-U version 9.1.0.0 or later
  6. 6. Restore the configuration backup if prompted or manually copy backed-up config files
  7. 7. Start the Serv-U service and verify it is running correctly
  8. 8. Test FTP functionality to ensure the server is operational
Caveat Review release notes for version 9.x as there may be configuration or feature changes from version 7.x; test in non-production environment first

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Serv U File Server Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing4.0 h
  • Review / QA1.0 h
9.0 hours of engineering $1,540
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2009-4006 in production — separate from our analysis above.

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What this is

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.

What belongs here
  • 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