How severe is CVE-2009-0091?

CVE-2009-0091 has a CVSS 2.0 base score of 9.3, rated critical severity.

Is CVE-2009-0091 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 26% (98th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2009-0091?

CVE-2009-0091 primarily affects Microsoft Windows 2000. In total, 26 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2009-0091?

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-2009-0091 published?

CVE-2009-0091 was published on 2009-10-14 and last updated on 2026-06-16.

CVE-2009-0091

CVE-2009-0091 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 26% places it in the 98th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-94.

Key facts

Severity: Critical (CVSS 2.0 base score 9.3)
EPSS exploit prediction: 26% (98th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-94
Affected product: Microsoft Windows 2000
Published: 2009-10-14
Last modified: 2026-06-16

Description

Microsoft .NET Framework 2.0, 2.0 SP1, and 3.5 does not properly enforce a certain type-equality constraint in .NET verifiable code, which allows remote attackers to execute arbitrary code via (1) a crafted XAML browser application (XBAP), (2) a crafted ASP.NET application, or (3) a crafted .NET Framework application, aka "Microsoft .NET Framework Type Verification Vulnerability."

Frequently asked questions

What is CVE-2009-0091?: Microsoft .NET Framework 2.0, 2.0 SP1, and 3.5 does not properly enforce a certain type-equality constraint in .NET verifiable code, which allows remote attackers to execute arbitrary code via (1) a crafted XAML browser application (XBAP), (2) a crafted ASP.NET application, or (3) a crafted .NET Framework application, aka "Microsoft .NET Framework Type Verification Vulnerability."
How severe is CVE-2009-0091?: CVE-2009-0091 has a CVSS 2.0 base score of 9.3, rated critical severity.
Is CVE-2009-0091 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 26% (98th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2009-0091?: CVE-2009-0091 primarily affects Microsoft Windows 2000. In total, 26 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2009-0091?: 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-2009-0091 published?: CVE-2009-0091 was published on 2009-10-14 and last updated on 2026-06-16.

References

Affected products (26)

cpe:2.3:o:microsoft:windows_2000:*:sp4:*:*:*:*:*:*
cpe:2.3:a:microsoft:.net_framework:1.1:sp1:*:*:*:*:*:*
cpe:2.3:a:microsoft:.net_framework:2.0:sp1:*:*:*:*:*:*
cpe:2.3:a:microsoft:.net_framework:2.0:sp2:*:*:*:*:*:*
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_server_2008:*:sp2:itanium:*:*:*:*:*
cpe:2.3:o:microsoft:windows_server_2008:*:sp2:x64:*:*:*:*:*
cpe:2.3:o:microsoft:windows_server_2008:-:sp2:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_server_2008:-:sp2:x86:*:*:*:*:*
cpe:2.3:a:microsoft:.net_framework:3.5:*:*:*:*:*:*:*
cpe:2.3:a:microsoft:.net_framework:3.5:sp1:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_vista:*:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_vista:*:*:x64:*:*:*:*:*
cpe:2.3:o:microsoft:windows_vista:*:sp1:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_vista:*:sp2:*:*:*:*:*:*
cpe:2.3:a:microsoft:.net_framework:2.0:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_7:-:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_server_2008:*:r2:itanium:*:*:*:*:*
cpe:2.3:o:microsoft:windows_server_2008:*:r2:x64:*:*:*:*:*
cpe:2.3:a:microsoft:.net_framework:1.0:sp3:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_xp:*:sp2:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_xp:*:sp3:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_xp:-:sp2:x64:*:*:*:*:*

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