Microsoft Security Advisory CVE-2026-45490 | .NET SDK Elevation of Privilege Vulnerability

## Executive summary

Microsoft is releasing this security advisory to provide information about a vulnerability in .NET 8.0, .NET 9.0, and .NET 10.0. This advisory also provides guidance on what developers can do to update their environments to remove this vulnerability.

An elevation of privilege vulnerability exists in the .NET SDK `dotnet.exe` workload command where one local user can exploit a weakly ACLed named pipe to perform arbitrary file creation or truncation as another local user. This only affects .NET on Windows operating systems.

## Announcement

Announcement for this issue can be found at https://github.com/dotnet/announcements/issues/403

## Mitigation factors

Microsoft has not identified any mitigating factors for this vulnerability.

## Affected software

* .NET 10.0 SDK

|Affected versions|Patched versions|
|-----------------|----------------|
|>= 10.0.100, <= 10.0.108|10.0.109|
|>= 10.0.300, <= 10.0.300|10.0.301|

* .NET 9.0 SDK

|Affected versions|Patched versions|
|-----------------|----------------|
|>= 9.0.100, <= 9.0.117|9.0.118|
|>= 9.0.300, <= 9.0.314|9.0.315|

* .NET 8.0 SDK

|Affected versions|Patched versions|
|-----------------|----------------|
|>= 8.0.100, <= 8.0.127|8.0.128|
|>= 8.0.400, <= 8.0.421|8.0.422|

## Affected Packages

The vulnerability does not affect Microsoft .NET packages.

## Advisory FAQ

### How do I know if I am affected?

If you have an SDK with a version listed, you're exposed to the vulnerability.

### How do I fix the issue?

1. To fix the issue please install the latest version of .NET 8.0 SDK, .NET 9.0 SDK, or .NET 10.0 SDK, as appropriate.

* If you're using .NET 8.0, you should download and install the latest .NET 8.0 SDK from https://dotnet.microsoft.com/download/dotnet-core/8.0.
* If you're using .NET 9.0, you should download and install the latest .NET 9.0 SDK from https://dotnet.microsoft.com/download/dotnet-core/9.0.
* If you're using .NET 10.0, you should download and install the latest .NET 10.0 SDK from https://dotnet.microsoft.com/download/dotnet-core/10.0.

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

```
.NET SDK:
Version: 10.0.100
Commit: 59db016f11

Runtime Environment:
OS Name: Windows
OS Version: 10.0.26100
OS Platform: Windows
RID: win-x64
Base Path: C:\Program Files\dotnet\sdk\10.0.100\

.NET SDKs installed:
10.0.100 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
Microsoft.AspNetCore.App 10.0.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.NETCore.App 10.0.0 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
```

Once you have installed the updated SDK, close any open command prompts, terminals, IDEs, or build agents that may have loaded an older `dotnet.exe`, and then re-run the affected `dotnet workload` command using the updated SDK.

## Other Information

### Reporting Security Issues

If you have found a potential security issue in .NET 8.0, .NET 9.0, or .NET 10.0, please email details to [secure@microsoft.com](mailto:secure@microsoft.com). Reports may qualify for the Microsoft .NET Core & .NET 5 Bounty. Details of the Microsoft .NET Bounty Program including terms and conditions are at https://aka.ms/corebounty.

### Support

You can ask questions about this issue on GitHub in the .NET GitHub organization. The main repos are located at https://github.com/dotnet/sdk. The Announcements repo (https://github.com/dotnet/Announcements) will contain this bulletin as an issue and will include a link to a discussion issue. You can ask questions in the linked discussion issue.

### Disclaimer

The information provided in this advisory is provided "as is" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.

### External Links

[CVE-2026-45490](https://www.cve.org/CVERecord?id=CVE-2026-45490)

### Acknowledgements

Ky0toFu, 41ae55e9310ff27fa6f26af4727e5590

### Revisions

V1.0 (June 9, 2026): Advisory published.