dbcve.org
Windows 2000Operating system · Microsoft

CVE-2002-1256

MEDIUM · 5.0 CVSS v2.0 Published 2002-12-23
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
59/100
Remediation priority · Elevated
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 signing capability in the Server Message Block (SMB) protocol in Microsoft Windows 2000 and Windows XP allows attackers to disable the digital signing settings in an SMB session to force the data to be sent unsigned, then inject data into the session without detection, e.g. by modifying group policy information sent from a domain controller.

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 · moderate confidence

This vulnerability allows attackers to downgrade SMB sessions by disabling digital signature requirements, then inject malicious data (such as modified group policy) into the SMB session without detection. The attack exploits the SMB handshake where signing settings can be coerced, enabling man-in-the-middle style injection of unauthorized content.

MitigationEnforce SMB signing requirements via Group Policy or registry settings (RequireSecuritySignature=1) on all Windows clients and servers, particularly domain controllers, to prevent acceptance of unsigned SMB traffic.

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 2000Operating system
Affected:all versions
Windows 2000 Terminal ServicesOperating 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
None
Integrity
Partial
Availability
None

AV:N/AC:L/Au:N/C:N/I:P/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 checks

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

  1. Identify the Windows version
    Run 'winver' or check System Properties to confirm the exact Windows version and build number
    Affected if The system is running Windows 2000 (any version) or Windows XP (any version)
  2. Check SMB signing registry setting
    Open Registry Editor and navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters. Look for the 'RequireSecuritySignature' value (DWORD). If absent or set to 0, SMB signing is not required.
    Affected if RequireSecuritySignature is missing or set to 0 (unsigned SMB is accepted)
  3. Check SMB client signing registry setting
    Navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanWorkstation\Parameters. Look for 'EnableSecuritySignature' (should be 1 for client) and 'RequireSecuritySignature' values.
    Affected if RequireSecuritySignature is absent or set to 0 on the client side
  4. Query current SMB signing configuration
    Run 'net config server' or 'net config workstation' from command prompt and look for 'Security signature' or 'Digital signing' settings in the output.
    Affected if The output shows SMB signing is disabled or not required
  5. Check Group Policy applied SMB settings
    Run 'gpresult /r' or 'rsop.msc' to review applied Group Policy, specifically under Computer Configuration > Windows Settings > Security Settings > Local Policies > Security Options. Look for 'Microsoft network client: Digitally sign communications (if server agrees)' and 'Microsoft network server: Digitally sign communications'.
    Affected if Policies are set to Disabled or 'If server agrees' rather than 'Always'

A system is affected if it runs Windows 2000 or Windows XP AND has SMB digital signing set to optional or disabled (not enforced), allowing potential man-in-the-middle injection of unsigned SMB traffic.

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.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Enforce SMB signing requirements via Group Policy or registry settings (RequireSecuritySignature=1) on all Windows clients and servers, particularly domain controllers, to prevent acceptance of unsigned SMB traffic.

Fix this in Windows 2000 Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA2.0 h
20.0 hours of engineering $3,500
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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-2002-1256 in production — separate from our analysis above.

No notes yet

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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
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  • Version or environment caveats, and links to real fixes
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