CVE-2026-87697 — Microsoft.WindowsDesktop.…
HIGHCVE-2026-87697 is a high-severity (CVSS 8.8) Deserialization of Untrusted Data vulnerability in Microsoft.WindowsDesktop.App.Runtime.win-arm64. A fix is available for Microsoft.WindowsDesktop.App.Runtime.win-arm64 — see the affected versions and patch details below.
Microsoft Security Advisory CVE-2026-87697 - .NET and Visual Studio Remote Code Execution Vulnerability
Real-World Exposure
Microsoft.WindowsDesktop.App.Runtime.win-arm64.NETMicrosoft.WindowsDesktop.App.Runtime.win-x64.NETMicrosoft.WindowsDesktop.App.Runtime.win-x86.NETMicrosoft.WindowsDesktop.App.Runtime.win-arm64.NETMicrosoft.WindowsDesktop.App.Runtime.win-x64.NETMicrosoft.WindowsDesktop.App.Runtime.win-x86.NETMicrosoft.WindowsDesktop.App.Runtime.win-arm64.NETMicrosoft.WindowsDesktop.App.Runtime.win-x64+4 moreReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects NuGet packages — download data is not available via public APIs for these ecosystems.
Description
Executive summary
Microsoft is releasing this security advisory to provide information about a vulnerability in Microsoft.WindowsDesktop.App.Runtime (WPF). This advisory also provides guidance on what developers can do to update their applications to remove this vulnerability.
WPF XPS synthetic hyperlinks exposed through UI Automation can bypass restrictive navigation checks and reach attacker-controlled content, enabling remote code execution after user interaction.
Announcement
Announcement for this issue can be found at https://github.com/dotnet/announcements/issues/471
CVSS Details
-
Version: 3.1
-
Severity: High
-
Score: 8.8
-
Vector:
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H -
Weakness: CWE-502 (Deserialization of Untrusted Data)
Affected Platforms
- Platforms: Windows
- Architectures: All
<a name="affected-packages"></a>Affected Packages
The vulnerability affects Microsoft .NET projects that use an affected package version listed below.
| Package name | Affected version | Patched version |
|---|---|---|
| Microsoft.WindowsDesktop.App.Runtime.win-arm64 | >= 9.0.0, <= 9.0.20 | 9.0.21 |
| Microsoft.WindowsDesktop.App.Runtime.win-x64 | >= 9.0.0, <= 9.0.20 | 9.0.21 |
| Microsoft.WindowsDesktop.App.Runtime.win-x86 | >= 9.0.0, <= 9.0.20 | 9.0.21 |
| Microsoft.WindowsDesktop.App.Runtime.win-arm64 | >= 8.0.0, <= 8.0.31 | 8.0.32 |
| Microsoft.WindowsDesktop.App.Runtime.win-x64 | >= 8.0.0, <= 8.0.31 | 8.0.32 |
| Microsoft.WindowsDesktop.App.Runtime.win-x86 | >= 8.0.0, <= 8.0.31 | 8.0.32 |
| Microsoft.WindowsDesktop.App.Runtime.win-arm64 | >= 11.0.0-preview.1, <= 11.0.0-rc.1 | 11.0.0-rc.2 |
| Microsoft.WindowsDesktop.App.Runtime.win-x64 | >= 11.0.0-preview.1, <= 11.0.0-rc.1 | 11.0.0-rc.2 |
| Microsoft.WindowsDesktop.App.Runtime.win-x86 | >= 11.0.0-preview.1, <= 11.0.0-rc.1 | 11.0.0-rc.2 |
| Microsoft.WindowsDesktop.App.Runtime.win-arm64 | >= 10.0.0, <= 10.0.12 | 10.0.13 |
| Microsoft.WindowsDesktop.App.Runtime.win-x64 | >= 10.0.0, <= 10.0.12 | 10.0.13 |
| Microsoft.WindowsDesktop.App.Runtime.win-x86 | >= 10.0.0, <= 10.0.12 | 10.0.13 |
Advisory FAQ
<a name="how-affected"></a>How do I know if I am affected?
If using a package listed in affected packages, you're exposed to the vulnerability.
<a name="how-fix"></a>How do I fix the issue?
- To fix the issue please install the latest version of .NET. 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.
- 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 --infocommand.
Once you have installed the updated runtime or SDK, restart your apps for the update to take effect.
Additionally, if you've deployed self-contained applications targeting any of the impacted versions, these applications are also vulnerable and must be recompiled and redeployed.
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 on GitHub in the .NET GitHub organization. The main repos are located at https://github.com/dotnet/runtime. 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
Acknowledgements
- 41ae55e9310ff27fa6f26af4727e5590
Revisions
V1.0 (10/13/2026): Advisory published.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| .NETNuGet | Microsoft.WindowsDesktop.App.Runtime.win-arm64 | ≥ 9.0.0&&< 9.0.21 | 9.0.21dotnet add package Microsoft.WindowsDesktop.App.Runtime.win-arm64 --version 9.0.21 |
| .NETNuGet | Microsoft.WindowsDesktop.App.Runtime.win-x64 | ≥ 9.0.0&&< 9.0.21 | 9.0.21dotnet add package Microsoft.WindowsDesktop.App.Runtime.win-x64 --version 9.0.21 |
| .NETNuGet | Microsoft.WindowsDesktop.App.Runtime.win-x86 | ≥ 9.0.0&&< 9.0.21 | 9.0.21dotnet add package Microsoft.WindowsDesktop.App.Runtime.win-x86 --version 9.0.21 |
| .NETNuGet | Microsoft.WindowsDesktop.App.Runtime.win-arm64 | ≥ 8.0.0&&< 8.0.32 | 8.0.32dotnet add package Microsoft.WindowsDesktop.App.Runtime.win-arm64 --version 8.0.32 |
| .NETNuGet | Microsoft.WindowsDesktop.App.Runtime.win-x64 | ≥ 8.0.0&&< 8.0.32 | 8.0.32dotnet add package Microsoft.WindowsDesktop.App.Runtime.win-x64 --version 8.0.32 |
| .NETNuGet | Microsoft.WindowsDesktop.App.Runtime.win-x86 | ≥ 8.0.0&&< 8.0.32 | 8.0.32dotnet add package Microsoft.WindowsDesktop.App.Runtime.win-x86 --version 8.0.32 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for Microsoft.WindowsDesktop.App.Runtime.win-arm64, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update Microsoft.WindowsDesktop.App.Runtime.win-arm64 to 9.0.21 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-87697 is resolved across your whole dependency graph.
Workarounds
Do not deserialise data from untrusted sources: where the format allows it, restrict deserialisation to an explicit allowlist of expected types, and prefer a data-only format (JSON, Protobuf) over one that can reconstruct arbitrary objects until you can upgrade.
Frequently Asked Questions
Is CVE-2026-87697 in your dependencies?
Find it across NuGet, including transitive dependencies.