CVE-2025-21171

Microsoft Security Advisory CVE-2025-21171 | .NET Remote Code Execution Vulnerability

<a name="executive-summary"></a>Executive summary

Microsoft is releasing this security advisory to provide information about a vulnerability in .NET 9.0. This advisory also provides guidance on what developers can do to update their applications to remove this vulnerability.

An attacker could exploit this vulnerability by sending a specially crafted request to the vulnerable web server.

Announcement

Announcement for this issue can be found at https://github.com/dotnet/runtime/issues/111423

<a name="mitigation-factors"></a>Mitigation factors

Microsoft has not identified any mitigating factors for this vulnerability.

<a name="affected-software"></a>Affected software

• Any .NET 9.0 application running on .NET 9.0.0 or earlier.

<a name="affected-packages"></a>Affected Packages

The vulnerability affects any Microsoft .NET project if it uses any of affected packages versions listed below

<a name=".NET 9"></a>.NET 9

Package name | Affected version | Patched version ------------ | ---------------- | ------------------------- Microsoft.NetCore.App.Runtime.linux-arm | >= 9.0.0, < 9.0.1 | 9.0.1 Microsoft.NetCore.App.Runtime.linux-arm64 | >= 9.0.0, < 9.0.1 | 9.0.1 Microsoft.NetCore.App.Runtime.linux-musl-arm | >= 9.0.0, < 9.0.1 | 9.0.1 Microsoft.NetCore.App.Runtime.linux-musl-arm64 | >= 9.0.0, < 9.0.1 | 9.0.1 Microsoft.NetCore.App.Runtime.linux-musl-x64 | >= 9.0.0, < 9.0.1 | 9.0.1 Microsoft.NetCore.App.Runtime.linux-x64 | >= 9.0.0, < 9.0.1 | 9.0.1 Microsoft.NetCore.App.Runtime.osx-arm64 | >= 9.0.0, < 9.0.1 | 9.0.1 Microsoft.NetCore.App.Runtime.osx-x64 | >= 9.0.0, < 9.0.1 | 9.0.1 Microsoft.NetCore.App.Runtime.win-arm | >= 9.0.0, < 9.0.1 | 9.0.1 Microsoft.NetCore.App.Runtime.win-arm64 | >= 9.0.0, < 9.0.1 | 9.0.1 Microsoft.NetCore.App.Runtime.win-x64 | >= 9.0.0, < 9.0.1 | 9.0.1 Microsoft.NetCore.App.Runtime.win-x86 | >= 9.0.0, < 9.0.1 | 9.0.1

Advisory FAQ

<a name="how-affected"></a>How do I know if I am affected?

If you have a runtime or SDK with a version listed, or an affected package listed in affected software or affected packages, you're exposed to the vulnerability.

<a name="how-fix"></a>How do I fix the issue?

1. To fix the issue please install the latest version of .NET 9.0. If you have installed one or more .NET SDKs through Visual Studio, Visual Studio will prompt you to update Visual Studio, which will also update your .NET SDKs.
2. If your application references the vulnerable package, update the package reference to the patched version.

• You can list the versions you have installed by running the dotnet --info command. You will see output like the following;

.NET SDK:
 Version:           9.0.100
 Commit:            59db016f11
 Workload version:  9.0.100-manifests.3068a692
 MSBuild version:   17.12.7+5b8665660

Runtime…

.NET Remote Code Execution Vulnerability

.NET is a managed-software framework. It implements a subset of the .NET framework APIs and several new APIs, and it includes a CLR implementation.

New versions of .NET that address a security vulnerability are now available. The updated versions are .NET SDK 9.0.102 and .NET Runtime 9.0.1.

Security Fix(es):

• dotnet: .NET Remote Code Execution Vulnerability (CVE-2025-21171)
• dotnet: .NET and Visual Studio Remote Code Execution Vulnerability (CVE-2025-21172)
• dotnet: .NET Elevation of Privilege Vulnerability (CVE-2025-21173)
• dotnet: .NET, .NET Framework, and Visual Studio Remote Code Execution Vulnerability (CVE-2025-21176)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.Security Fix(es):

• dotnet: .NET Elevation of Privilege Vulnerability (CVE-2025-21173)
• dotnet: .NET, .NET Framework, and Visual Studio Remote Code Execution Vulnerability (CVE-2025-21176)
• dotnet: .NET and Visual Studio Remote Code Execution Vulnerability (CVE-2025-21172)
• dotnet: .NET Remote Code Execution Vulnerability (CVE-2025-21171)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

.NET Remote Code Execution Vulnerability

.NET Remote Code Execution Vulnerability

.NET Remote Code Execution Vulnerability

.NET is a managed-software framework. It implements a subset of the .NET framework APIs and several new APIs, and it includes a CLR implementation.

New versions of .NET that address a security vulnerability are now available. The updated versions are .NET SDK 9.0.102 and .NET Runtime 9.0.1.

Security Fix(es):

• dotnet: .NET Remote Code Execution Vulnerability (CVE-2025-21171)
• dotnet: .NET and Visual Studio Remote Code Execution Vulnerability (CVE-2025-21172)
• dotnet: .NET Elevation of Privilege Vulnerability (CVE-2025-21173)
• dotnet: .NET, .NET Framework, and Visual Studio Remote Code Execution Vulnerability (CVE-2025-21176)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.Security Fix(es):

• dotnet: .NET Elevation of Privilege Vulnerability (CVE-2025-21173)

• dotnet: .NET, .NET Framework, and Visual Studio Remote Code Execution Vulnerability (CVE-2025-21176)

• dotnet: .NET and Visual Studio Remote Code Execution Vulnerability (CVE-2025-21172)

• dotnet: .NET Remote Code Execution Vulnerability (CVE-2025-21171)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

It was discovered that .NET did not properly handle input provided to its Convert.TryToHexString method. An attacker could possibly use this issue to execute arbitrary code. (CVE-2025-21171)

It was discovered that .NET did not properly handle an integer overflow when processing certain specially crafted files. An attacker could possibly use this issue to execute arbitrary code. (CVE-2025-21172)

Daniel Plaisted and Noah Gilson discovered that .NET insecurely handled temporary file usage which could result in malicious package dependency injection. An attacker could possibly use this issue to elevate privileges. (CVE-2025-21173)

It was discovered that .NET did not properly perform input data validation when processing certain specially crafted files. An attacker could possibly use this issue to execute arbitrary code. (CVE-2025-21176)