CVE-2026-70197: .NET System.Net.Sockets out-of-bounds write in IPv4/IPv6 datagram handling

CVE-2026-70197 · Severity: high · CVSS 8.1 · Published 2026-10-13

.NET is a framework that runs applications on Windows, and this vulnerability affects the networking component that handles datagram communication. An attacker can exploit a flaw where reusing certain socket buffers between IPv4 and IPv6 results in an undersized memory allocation, allowing them to write beyond the allocated memory and execute arbitrary code on a Windows system. This requires specific application code patterns but poses a critical risk to any application using affected .NET versions.

Technologies: Microsoft .Net, Microsoft Visual Studio, Microsoft.NetCore.App.Runtime.win-arm64 (NuGet), Microsoft.NetCore.App.Runtime.win-x64 (NuGet), Microsoft.NetCore.App.Runtime.win-x86 (NuGet). Vendors: Microsoft, NuGet.

Quick answers

Is CVE-2026-70197 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-70197 being exploited in the wild.
How severe is CVE-2026-70197?
High severity, with a CVSS score of 8.1, published 13 October 2026.
Which products and versions are affected?
Microsoft .Net 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 Visual Studio versions using affected .NET SDKs; Microsoft.NetCore.App.Runtime.win-arm64 (NuGet) >= 8.0.0, <= 8.0.31, ECOSYSTEM:introduced=8.0.0,fixed=8.0.32; Microsoft.NetCore.App.Runtime.win-x64 (NuGet) >= 8.0.0, <= 8.0.31, ECOSYSTEM:introduced=8.0.0,fixed=8.0.32; and 1 more.
Is there a fix for CVE-2026-70197?
Yes. Microsoft.NetCore.App.Runtime.win-arm64 (NuGet): upgrade to 8.0.32 or later; Microsoft.NetCore.App.Runtime.win-x64 (NuGet): upgrade to 8.0.32 or later; Microsoft.NetCore.App.Runtime.win-x86 (NuGet): upgrade to 8.0.32 or later. Until then: Update .NET runtime or SDK to the patched versions and restart applications. If self-contained applications targeting affected versions have been deployed, they must be recompiled with the patched runtime and redeployed. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-70197 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-70197?
Check whether you run Microsoft .Net, Microsoft Visual Studio, Microsoft.NetCore.App.Runtime.win-arm64 (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.NetCore.App.Runtime.win-arm64 (NuGet): upgrade to 8.0.32 or later
    dotnet add package Microsoft.NetCore.App.Runtime.win-arm64 --version 8.0.32
  • Microsoft.NetCore.App.Runtime.win-x64 (NuGet): upgrade to 8.0.32 or later
    dotnet add package Microsoft.NetCore.App.Runtime.win-x64 --version 8.0.32
  • Microsoft.NetCore.App.Runtime.win-x86 (NuGet): upgrade to 8.0.32 or later
    dotnet add package Microsoft.NetCore.App.Runtime.win-x86 --version 8.0.32

Update .NET runtime or SDK to the patched versions and restart applications. If self-contained applications targeting affected versions have been deployed, they must be recompiled with the patched runtime and redeployed.

Technical details

The vulnerability is an out-of-bounds write (CWE-787) in System.Net.Sockets on Windows when an application reuses a SocketAsyncEventArgs instance across IPv4 and IPv6 datagram sockets, resulting in a cached native address buffer that is undersized. An unauthenticated attacker can trigger this via network communication to perform an out-of-bounds write during ReceiveFromAsync operations, leading to remote code execution. The flaw affects .NET 8.0 through 10.0 and 11.0 preview versions, with fixes available in 8.0.32, 9.0.21, 10.0.13, and 11.0.0-rc.2.

Affected products

  • Microsoft .NET 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 Visual Studio versions using affected .NET SDKs

Identifiers

  • CVE-2026-70197
  • GHSA-4mpw-cpwj-hxxj

Timeline

  • 2026-10-13: disclosed

This page as Markdown. Free to reuse under CC BY 4.0 with a link back.