CVE-2009-0550

CVE-2009-0550 is a critical-severity vulnerability in Microsoft Windows 2000 with a CVSS 2.0 base score of 9.3. Its EPSS exploit-prediction score of 12% places it in the 96th percentile, indicating an elevated likelihood of exploitation.

Key facts

• Severity: Critical (CVSS 2.0 base score 9.3)
• EPSS exploit prediction: 12% (96th percentile)
• Actively exploited: Not listed in CISA KEV
• Affected product: Microsoft Windows 2000
• Published: 2009-04-15
• Last modified: 2026-06-16

Description

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."

Frequently asked questions

What is CVE-2009-0550?

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."

How severe is CVE-2009-0550?

CVE-2009-0550 has a CVSS 2.0 base score of 9.3, rated critical severity.

Is CVE-2009-0550 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 12% (96th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2009-0550?

CVE-2009-0550 primarily affects Microsoft Windows 2000. In total, 24 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2009-0550?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2009-0550 published?

CVE-2009-0550 was published on 2009-04-15 and last updated on 2026-06-16.

References

• http://blogs.technet.com/srd/archive/2009/04/14/ntlm-credential-reflection-updates-for-http-clients.aspx
• http://osvdb.org/53619
• http://secunia.com/advisories/34677
• http://secunia.com/advisories/34678
• http://support.avaya.com/elmodocs2/security/ASA-2009-133.htm
• http://support.nortel.com/go/main.jsp?cscat=BLTNDETAIL&id=871138
• http://www.securityfocus.com/bid/34439
• http://www.securitytracker.com/id?1022041
• http://www.us-cert.gov/cas/techalerts/TA09-104A.html
• http://www.vupen.com/english/advisories/2009/1027
• http://www.vupen.com/english/advisories/2009/1028
• https://docs.microsoft.com/en-us/security-updates/securitybulletins/2009/ms09-013
• https://docs.microsoft.com/en-us/security-updates/securitybulletins/2009/ms09-014
• https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A5320
• https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A6233
• https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A7569

Affected products (24)

• cpe:2.3:o:microsoft:windows_2000:*:sp4:*:*:*:*:*:*
• cpe:2.3:o:microsoft:windows_server_2003:*:*:*:*:*:*:*:*
• cpe:2.3:o:microsoft:windows_server_2003:*:sp1:*:*:*:*:*:*
• cpe:2.3:o:microsoft:windows_server_2003:*:sp1:itanium:*:*:*:*:*
• cpe:2.3:o:microsoft:windows_server_2003:*:sp2:*:*:*:*:*:*
• cpe:2.3:o:microsoft:windows_server_2008:*:*:itanium:*:*:*:*:*
• cpe:2.3:o:microsoft:windows_server_2008:*:*:x32:*:*:*:*:*
• cpe:2.3:o:microsoft:windows_server_2008:*:*:x64:*:*:*:*:*
• cpe:2.3:o:microsoft:windows_vista:*:*:x64:*:*:*:*:*
• cpe:2.3:o:microsoft:windows_vista:*:sp1:*:*:*:*:*:*
• cpe:2.3:o:microsoft:windows_vista:gold:*:*:*:*:*:*:*
• cpe:2.3:o:microsoft:windows_xp:*:*:pro_x64:*:*:*:*:*
• cpe:2.3:o:microsoft:windows_xp:*:sp2:*:*:*:*:*:*
• cpe:2.3:o:microsoft:windows_xp:*:sp2:pro_x64:*:*:*:*:*
• cpe:2.3:o:microsoft:windows_xp:*:sp3:*:*:*:*:*:*
• cpe:2.3:a:microsoft:ie:6.0:sp1:*:*:*:*:*:*
• cpe:2.3:a:microsoft:internet_explorer:5.01:sp4:*:*:*:*:*:*
• cpe:2.3:a:microsoft:internet_explorer:6:*:*:*:*:*:*:*
• cpe:2.3:a:microsoft:internet_explorer:7:*:*:*:*:*:*:*
• cpe:2.3:o:microsoft:windows_server_2008:*:*:*:*:*:*:*:*
• cpe:2.3:o:microsoft:windows_server_2008:*:*:32_bit:*:*:*:*:*
• cpe:2.3:o:microsoft:windows_vista:*:*:*:*:*:*:*:*
• cpe:2.3:o:microsoft:windows_xp:*:*:x64:*:*:*:*:*
• cpe:2.3:o:microsoft:windows_xp:*:sp2:x64:*:*:*:*:*

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