dbcve.org
Windows 2003 ServerOperating system · Microsoft

CVE-2011-0661

HIGH · 10.0 CVSS v2.0 Published 2011-04-13
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
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
The SMB Server service in Microsoft Windows XP SP2 and SP3, Windows Server 2003 SP2, Windows Vista SP1 and SP2, Windows Server 2008 Gold, SP2, R2, and R2 SP1, and Windows 7 Gold and SP1 does not properly validate fields in SMB requests, which allows remote attackers to execute arbitrary code via a malformed request in a (1) SMBv1 or (2) SMBv2 packet, aka "SMB Transaction Parsing Vulnerability."

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

SMB Transaction Parsing Vulnerability in Microsoft Windows allows remote unauthenticated attackers to execute arbitrary code via malformed SMBv1 or SMBv2 packets. The SMB Server service fails to properly validate fields in SMB transaction requests, leading to memory corruption that can be exploited for code execution.

MitigationApply Microsoft security updates (MS11-020) to all affected Windows systems. If immediate patching is not possible, block SMB ports (445/139) at the network perimeter and disable SMBv1 via registry or group policy.

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
Windows 2003 ServerOperating system
Affected:all versions
Windows 7Operating system
Affected:all versions
Windows Server 2003Operating system
Affected:all versions
Windows Server 2008Operating system
Affected:all versions= r2
Windows VistaOperating system
Affected:all versions
Windows XpOperating system
Affected:all versions

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. Identify Windows version
    Run 'winver' or 'systeminfo | findstr /B /C:"OS Name" /C:"OS Version"' to determine the installed Windows version
    Affected if The version is Windows XP, Vista, Windows 7, Windows Server 2003, Windows Server 2008, or Windows Server 2008 R2 (any edition)
  2. Verify SMB Server service status
    Run 'services.msc' and locate 'Server' service, or run 'sc query server' from command prompt
    Affected if The Server service is running (required for SMB to be accessible)
  3. Check if SMBv1 protocol is enabled
    Check registry key 'HKLM\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters' for 'SMB1' value (DWORD). If value is 1, SMBv1 is enabled. Also run 'Get-WindowsOptionalFeature -Online -FeatureName SMB1Protocol' on newer systems.
    Affected if SMBv1 is enabled (value set to 1 or feature not disabled) - this increases attack surface significantly
  4. Verify MS11-020 security update is installed
    Run 'wmic qfe list' or check 'C:\Windows\SoftwareDistribution\Download' for update KB2490606 (the patch for this CVE)
    Affected if The security update KB2490606 is NOT installed - system remains vulnerable

A system is affected if it runs any affected Windows version (XP/Vista/7/Server 2003/2008/2008 R2), has the SMB Server service running, lacks the MS11-020 update (KB2490606), or has SMBv1 enabled.

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

Apply Microsoft security updates (MS11-020) to all affected Windows systems. If immediate patching is not possible, block SMB ports (445/139) at the network perimeter and disable SMBv1 via registry or group policy.

Recommended fix Moderate confidence

Replace affected systems with Windows 10/11 or Windows Server 2012 or later

  1. Identify all affected Windows systems in your environment (Windows XP, Windows Server 2003, Windows Vista, Windows 7, Windows Server 2008/R2)
  2. Since this is a critical RCE vulnerability (CVSS 10) in SMB service, prioritize patching or replacement immediately
  3. For Windows XP and Windows Server 2003: These operating systems reached end of support. Microsoft no longer provides security updates. Replace these systems with supported operating systems (Windows Server 2012 or later, Windows 10/11)
  4. For Windows Vista: Reached end of support in April 2017. Replace with supported operating system
  5. For Windows 7 and Windows Server 2008 R2: Extended support ended in January 2020. Replace with supported operating systems
  6. For Windows Server 2008 R2: Extended support ended in January 2020. Replace with supported operating systems
  7. If immediate replacement is not possible, consider network segmentation to isolate vulnerable systems and block SMB ports (139, 445) from untrusted networks
  8. Apply any available Microsoft updates from Windows Update for systems still under support
Caveat Legacy applications requiring Windows XP/2003/Vista may need modernization or replacement; some applications may not be compatible with newer OS versions

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

Fix this in Windows 2003 Server Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,930
Get help mitigating

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,088.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2011-0661 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

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-2011-0661 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

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