# CVE-2026-83520: .NET WindowsDesktop.App.Runtime XAML deserialization RCE

Source: https://junglewise.ai/threats/cve-2026-83520-microsoft-security-advisory-net-and-visual-studio-remote-code  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-13. Updated: 2026-10-13  
License: CC BY 4.0 with a link back

CVE-2026-83520 · Severity: high · CVSS 8.8 · Published 2026-10-13

Microsoft .NET's Windows Desktop runtime, which powers graphical applications built with WPF, contains a flaw in how it processes XAML markup that can allow remote code execution. An attacker can craft a malicious XAML file or navigate a user to a malicious website that triggers unsafe deserialization, leading to complete compromise of the affected application and system.

Technologies: [Microsoft.WindowsDesktop.App.Runtime.win-arm64 (NuGet)](https://junglewise.ai/threats/technologies/microsoft-windowsdesktop-app-runtime-win-arm64), [Microsoft.WindowsDesktop.App.Runtime.win-x64 (NuGet)](https://junglewise.ai/threats/technologies/microsoft-windowsdesktop-app-runtime-win-x64), [Microsoft.WindowsDesktop.App.Runtime.win-x86 (NuGet)](https://junglewise.ai/threats/technologies/microsoft-windowsdesktop-app-runtime-win-x86). Vendors: [Microsoft](https://junglewise.ai/threats/vendors/microsoft), [NuGet](https://junglewise.ai/threats/vendors/nuget).

## Quick answers

**Is CVE-2026-83520 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-83520 being exploited in the wild.

**How severe is CVE-2026-83520?** High severity, with a CVSS score of 8.8, published 13 October 2026.

**Which products and versions are affected?** Microsoft .NET WindowsDesktop.App.Runtime 8.0.0 through 8.0.31, 9.0.0 through 9.0.20, 10.0.0 through 10.0.12, 11.0.0-preview.1 through 11.0.0-rc.1; Microsoft.WindowsDesktop.App.Runtime.win-arm64 (NuGet) >= 11.0.0-preview.1, <= 11.0.0-rc.1, ECOSYSTEM:introduced=11.0.0-preview.1,fixed=11.0.0-rc.2; Microsoft.WindowsDesktop.App.Runtime.win-x64 (NuGet) >= 11.0.0-preview.1, <= 11.0.0-rc.1, ECOSYSTEM:introduced=11.0.0-preview.1,fixed=11.0.0-rc.2; Microsoft.WindowsDesktop.App.Runtime.win-x86 (NuGet) >= 11.0.0-preview.1, <= 11.0.0-rc.1, ECOSYSTEM:introduced=11.0.0-preview.1,fixed=11.0.0-rc.2.

**Is there a fix for CVE-2026-83520?** Yes. Microsoft.WindowsDesktop.App.Runtime.win-arm64 (NuGet): upgrade to 11.0.0-rc.2 or later; Microsoft.WindowsDesktop.App.Runtime.win-x64 (NuGet): upgrade to 11.0.0-rc.2 or later; Microsoft.WindowsDesktop.App.Runtime.win-x86 (NuGet): upgrade to 11.0.0-rc.2 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-83520 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-83520?** Check whether you run Microsoft .NET WindowsDesktop.App.Runtime, Microsoft.WindowsDesktop.App.Runtime.win-arm64 (NuGet), Microsoft.WindowsDesktop.App.Runtime.win-x64 (NuGet) or one of the others listed at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- Microsoft.WindowsDesktop.App.Runtime.win-arm64 (NuGet): upgrade to 11.0.0-rc.2 or later

  ```sh
  dotnet add package Microsoft.WindowsDesktop.App.Runtime.win-arm64 --version 11.0.0-rc.2
  ```

- Microsoft.WindowsDesktop.App.Runtime.win-x64 (NuGet): upgrade to 11.0.0-rc.2 or later

  ```sh
  dotnet add package Microsoft.WindowsDesktop.App.Runtime.win-x64 --version 11.0.0-rc.2
  ```

- Microsoft.WindowsDesktop.App.Runtime.win-x86 (NuGet): upgrade to 11.0.0-rc.2 or later

  ```sh
  dotnet add package Microsoft.WindowsDesktop.App.Runtime.win-x86 --version 11.0.0-rc.2
  ```


## Technical details

The vulnerability stems from deserialization of untrusted XAML and XPS data (CWE-502), where unsafe URI fetching, unrestricted hyperlink navigation, and unprotected TrueType font loading can be exploited. An attacker with network access can deliver a malicious XAML file or craft a navigation action requiring only user interaction (clicking a link). The fixes restrict URI fetching, add XAML nesting-depth limits, enable font protection, and prevent caching of untrusted DNS decisions.

## Affected products

- Microsoft .NET WindowsDesktop.App.Runtime 8.0.0 through 8.0.31, 9.0.0 through 9.0.20, 10.0.0 through 10.0.12, 11.0.0-preview.1 through 11.0.0-rc.1

## Identifiers

- CVE-2026-83520
- GHSA-4w5f-7jp2-w48g

## Timeline

- 2026-10-13: disclosed

## Related threats

- [.NET WindowsDesktop.App.Runtime deserialization remote code execution](https://junglewise.ai/threats/cve-2026-70035-microsoft-security-advisory-net-and-visual-studio-remote-code)
- [Microsoft .NET and Visual Studio WPF heap out-of-bounds write](https://junglewise.ai/threats/cve-2026-70007-microsoft-security-advisory-net-and-visual-studio-remote-code)
- [.NET WPF XPS synthetic hyperlinks remote code execution](https://junglewise.ai/threats/cve-2026-87697-microsoft-security-advisory-net-and-visual-studio-remote-code)
- [Microsoft .NET WindowsDesktop.App.Runtime heap buffer overflow in WPF shader parsing](https://junglewise.ai/threats/cve-2026-96224-microsoft-security-advisory-net-and-visual-studio-remote-code)
- [Microsoft .NET Windows Desktop App Runtime integer overflow in glyph processing](https://junglewise.ai/threats/cve-2026-85363-microsoft-security-advisory-net-and-visual-studio-remote-code)