Microsoft Security Advisory CVE-2026-105544 - .NET Elevation of Privilege Vulnerability

Executive summary

Microsoft is releasing this security advisory to provide information about a vulnerability in .NET. This advisory provides guidance on updating affected applications and components.

The VSTest artifact postprocessor can consume a forged executionComplete.json from another local user and execute attacker-controlled output handling.

Announcement

Announcement for this issue can be found at https://github.com/dotnet/announcements/issues/517

CVSS Details

• Version: 3.1
• Severity: High
• Score: 7.5 (base score)
• Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:C/C:H/I:H/A:H/E:U/RL:O/RC:C
• Weakness: CWE-284

Affected Platforms

• Platforms: Windows, Linux, macOS
• Architectures: All

Affected Packages

The tables list affected versions of Microsoft.TestPlatform.CLI and their patched versions. The VSTest CLI is also bundled in the .NET SDK; SDK versions are listed separately below. Updating a separately installed CLI package does not replace the SDK-bundled test runner.

Microsoft.TestPlatform.CLI is affected starting with 17.2.0-preview-20220301-01, including the first stable release, 17.2.0. Use a patched version listed below for a compatible servicing line.

VSTest NuGet package

Stable 18.10.1 remains affected; use Microsoft.TestPlatform.CLI 18.10.2 on that servicing line.

Other affected VSTest NuGet versions

These releases have no same-line fixed package in this update. Move to a compatible fixed servicing line listed above.

Affected VSTest prerelease versions

The following table applies to Microsoft.TestPlatform.CLI.

Fixed .NET SDK deliveries

Earlier SDKs in these serviced feature bands must be updated. The first .NET 11 general-availability SDK is fixed; its earlier preview and release-candidate SDKs require an update to 11.0.100.

Advisory FAQ

How do I know if I am affected?

Check the version of Microsoft.TestPlatform.CLI used by your standalone VSTest installation.

Run dotnet --list-sdks to list installed SDKs and dotnet --version from the project directory to identify the selected SDK, including any global.json selection.

How do I fix the issue?

For standalone VSTest CLI installations, replace Microsoft.TestPlatform.CLI with its patched version listed above. For releases without a same-line fix, use a compatible fixed servicing line listed above.

Install a fixed SDK listed above and ensure test invocations select it. Updating a separately installed CLI package does not replace VSTest embedded in an older SDK.

Other Information

Reporting Security Issues

If you have found a potential security issue in a supported version of .NET, please report it to the Microsoft Security Response Center (MSRC) via the MSRC Researcher Portal. Further information can be found in the MSRC Report an Issue FAQ.

Security reports made through MSRC may qualify for the Microsoft .NET 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 in the VSTest repository at https://github.com/microsoft/vstest. 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-2026-105544

Acknowledgements

• Weeraphat Srisutham
• Ky0toFu

Revisions

V1.0 (November 10, 2026): Advisory published.