dbcve.org
Windows 2000Operating system · Microsoft

CVE-2009-0550

HIGH · 9.3 CVSS v2.0 Published 2009-04-15
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
Windows HTTP Services (aka WinHTTP) in Microsoft Windows 2000 SP4, XP SP2 and SP3, Server 2003 SP1 and SP2, Vista Gold and SP1, and Server 2008; and WinINet in Microsoft Internet Explorer 5.01 SP4, 6 SP1, 6 and 7 on Windows XP SP2 and SP3, 6 and 7 on Windows Server 2003 SP1 and SP2, 7 on Windows Vista Gold and SP1, and 7 on Windows Server 2008; allows remote web servers to capture and replay NTLM credentials, and execute arbitrary code, via vectors related to absence of a "credential-reflection protections" opt-in step, aka "Windows HTTP Services Credential Reflection Vulnerability" and "WinINet Credential Reflection 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

This is a credential reflection vulnerability in Windows HTTP Services (WinHTTP) and WinINet that allows remote malicious web servers to capture and replay NTLM authentication credentials, potentially leading to arbitrary code execution. The vulnerability stems from the absence of built-in credential-reflection protections that should have been implemented as an opt-in security feature.

MitigationApply the relevant Microsoft security patches (MS09-013) and disable NTLM authentication or enable extended protection for authentication where possible to prevent credential reflection attacks.

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 Server 2003Operating system
Affected:all versions
Windows Server 2008Operating system
Affected:all versions
Windows VistaOperating system
Affected:all versions= gold
Windows XpOperating system
Affected:all versions
IeApplication
Affected:= 6.0
Internet ExplorerApplication
Affected:= 5.01= 6= 7

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
M
Authentication
None
Confidentiality
Complete
Integrity
Complete
Availability
Complete

AV:N/AC:M/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 check system properties to confirm the Windows version. Affected versions are Windows 2000, Windows XP, Windows Server 2003, Windows Vista, and Windows Server 2008.
    Affected if The system is running an unpatched version of Windows 2000, XP, Server 2003, Vista, or Server 2008.
  2. Check if MS09-013 security update is installed
    Open Control Panel > Programs and Features > View installed updates, then search for 'KB958469' or 'MS09-013'. Alternatively, run 'wmic qfe list' or check Windows Update history.
    Affected if The MS09-013 update (KB958469) is NOT installed on the affected Windows version.
  3. Verify Internet Explorer version
    Open IE, go to Help > About Internet Explorer, or check 'HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer' in the registry.
    Affected if Internet Explorer version is 5.01, 6, or 7 on an affected Windows system without the patch.
  4. Determine if NTLM authentication is enabled in WinHTTP
    Check registry key 'HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WinHttpAutoProxySvc' and review WinHTTP proxy settings. Use 'netsh winhttp show proxy' to check proxy configuration.
    Affected if WinHTTP is configured to use system proxy and NTLM authentication is permitted to remote servers.
  5. Check if Extended Protection for Authentication is available
    Check registry key 'HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa' for 'SupportsExtendedProtection' DWORD value. On affected systems, this protection is absent or insufficient.
    Affected if Extended Protection for Authentication is not enabled or the system lacks this security feature (typical of unpatched Windows 2000/XP/Server 2003/Vista).

The system is affected if it runs an unpatched Windows 2000/XP/Vista/Server 2003/Server 2008 with IE 5.01-7 and has NTLM authentication enabled, allowing credential reflection attacks.

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 the relevant Microsoft security patches (MS09-013) and disable NTLM authentication or enable extended protection for authentication where possible to prevent credential reflection attacks.

Recommended fix High confidence

Windows 7 with current security updates (or Windows 10/11 for current systems); for legacy systems: Windows Server 2008 R2 or later

  1. Identify all affected systems running Windows 2000, Windows XP, Windows Server 2003, Windows Vista, or Windows Server 2008 that have not been patched for MS09-013
  2. For Windows XP SP2/SP3, Windows Server 2003 SP1/SP2, Windows Vista SP1, and Windows Server 2008: Apply Microsoft Security Bulletin MS09-013 (Windows HTTP Services Vulnerability)
  3. If running Windows 2000 SP4: Upgrade to a supported operating system as Windows 2000 reached end-of-life and no longer receives security updates
  4. After patching, verify that WinHTTP credential reflection protections are enabled by checking registry settings or applying the NTLM authentication hardening as documented in MS09-013
  5. Test that applications relying on WinHTTP or WinINet authentication continue to function properly post-patch
Caveat Windows 2000 is end-of-life with no patch path; ensure compatibility testing for applications on upgraded systems as NTLM authentication behavior may change

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

Fix this in Windows 2000 Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing4.0 h
  • Review / QA2.0 h
18.0 hours of engineering $3,200
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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-2009-0550 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
  • 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