CVE-2026-70194: .NET TLS client certificate verification bypass

CVE-2026-70194 · Severity: medium · CVSS 6.5 · Published 2026-10-13

.NET 11 implements post-handshake TLS client authentication as part of mutual-authentication security controls. A flaw in System.Net.Security fails to properly verify client certificates in certain scenarios, allowing an attacker to bypass mutual-authentication requirements and communicate without providing valid credentials.

Technologies: Microsoft .Net, Microsoft.NetCore.App.Runtime.linux-arm (NuGet), Microsoft.NetCore.App.Runtime.linux-arm64 (NuGet), Microsoft.NetCore.App.Runtime.linux-musl-arm (NuGet), Microsoft.NetCore.App.Runtime.linux-musl-arm64 (NuGet), Microsoft.NetCore.App.Runtime.linux-musl-x64 (NuGet), Microsoft.NetCore.App.Runtime.linux-x64 (NuGet), Microsoft.NetCore.App.Runtime.osx-arm64 (NuGet), Microsoft.NetCore.App.Runtime.osx-x64 (NuGet). Vendors: Microsoft, NuGet.

Quick answers

Is CVE-2026-70194 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-70194 being exploited in the wild.
How severe is CVE-2026-70194?
Medium severity, with a CVSS score of 6.5, published 13 October 2026.
Which products and versions are affected?
Microsoft .Net 11.0.0-preview.1 through 11.0.0-rc.1; Microsoft.NetCore.App.Runtime.linux-arm (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.NetCore.App.Runtime.linux-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.NetCore.App.Runtime.linux-musl-arm (NuGet) >= 11.0.0-preview.1, <= 11.0.0-rc.1, ECOSYSTEM:introduced=11.0.0-preview.1,fixed=11.0.0-rc.2; and 5 more.
Is there a fix for CVE-2026-70194?
Yes. Microsoft.NetCore.App.Runtime.linux-arm (NuGet): upgrade to 11.0.0-rc.2 or later; Microsoft.NetCore.App.Runtime.linux-arm64 (NuGet): upgrade to 11.0.0-rc.2 or later; Microsoft.NetCore.App.Runtime.linux-musl-arm (NuGet): upgrade to 11.0.0-rc.2 or later; Microsoft.NetCore.App.Runtime.linux-musl-arm64 (NuGet): upgrade to 11.0.0-rc.2 or later; Microsoft.NetCore.App.Runtime.linux-musl-x64 (NuGet): upgrade to 11.0.0-rc.2 or later; Microsoft.NetCore.App.Runtime.linux-x64 (NuGet): upgrade to 11.0.0-rc.2 or later; Microsoft.NetCore.App.Runtime.osx-arm64 (NuGet): upgrade to 11.0.0-rc.2 or later; Microsoft.NetCore.App.Runtime.osx-x64 (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-2026-70194 attacked?
It is attacked over the network.
Am I affected by CVE-2026-70194?
Check whether you run Microsoft .Net, Microsoft.NetCore.App.Runtime.linux-arm (NuGet), Microsoft.NetCore.App.Runtime.linux-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.linux-arm (NuGet): upgrade to 11.0.0-rc.2 or later
    dotnet add package Microsoft.NetCore.App.Runtime.linux-arm --version 11.0.0-rc.2
  • Microsoft.NetCore.App.Runtime.linux-arm64 (NuGet): upgrade to 11.0.0-rc.2 or later
    dotnet add package Microsoft.NetCore.App.Runtime.linux-arm64 --version 11.0.0-rc.2
  • Microsoft.NetCore.App.Runtime.linux-musl-arm (NuGet): upgrade to 11.0.0-rc.2 or later
    dotnet add package Microsoft.NetCore.App.Runtime.linux-musl-arm --version 11.0.0-rc.2
  • Microsoft.NetCore.App.Runtime.linux-musl-arm64 (NuGet): upgrade to 11.0.0-rc.2 or later
    dotnet add package Microsoft.NetCore.App.Runtime.linux-musl-arm64 --version 11.0.0-rc.2
  • Microsoft.NetCore.App.Runtime.linux-musl-x64 (NuGet): upgrade to 11.0.0-rc.2 or later
    dotnet add package Microsoft.NetCore.App.Runtime.linux-musl-x64 --version 11.0.0-rc.2
  • Microsoft.NetCore.App.Runtime.linux-x64 (NuGet): upgrade to 11.0.0-rc.2 or later
    dotnet add package Microsoft.NetCore.App.Runtime.linux-x64 --version 11.0.0-rc.2
  • Microsoft.NetCore.App.Runtime.osx-arm64 (NuGet): upgrade to 11.0.0-rc.2 or later
    dotnet add package Microsoft.NetCore.App.Runtime.osx-arm64 --version 11.0.0-rc.2
  • Microsoft.NetCore.App.Runtime.osx-x64 (NuGet): upgrade to 11.0.0-rc.2 or later
    dotnet add package Microsoft.NetCore.App.Runtime.osx-x64 --version 11.0.0-rc.2

Technical details

The vulnerability is an improper certificate validation flaw (CWE-295) in .NET 11's System.Net.Security library affecting post-handshake TLS client authentication. It allows an attacker on the network to bypass mutual-authentication requirements by presenting an invalid or missing client certificate that fails to be verified. A fix is available in version 11.0.0-rc.2 and later.

Affected products

  • Microsoft .NET 11.0.0-preview.1 through 11.0.0-rc.1

Identifiers

  • CVE-2026-70194
  • GHSA-fqpq-cx42-9jmm

Timeline

  • 2026-10-13: disclosed

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