CVE-2026-69651: Inefficient algorithmic complexity in .NET allows an unauthorized attacker to deny service over a network.

CVE-2026-69651 · Severity: high · CVSS 7.5 · Published 2026-10-13

.NET is a framework that developers use to build applications on Windows, Linux, and macOS. A flaw in its XML cryptography handling allows an attacker to send a specially crafted XML document that causes an application to consume excessive CPU and memory, resulting in a denial of service. Applications processing untrusted signed XML are at risk.

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), 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-2026-69651 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-69651 being exploited in the wild.
How severe is CVE-2026-69651?
High severity, with a CVSS score of 7.5, published 13 October 2026.
Which products and versions are affected?
Microsoft .Net 8.0.0–8.0.31, 9.0.0–9.0.20, 10.0.0–10.0.12, 11.0.0-preview.1–11.0.0-rc.1; Microsoft.NetCore.App.Runtime.linux-arm (NuGet) >= 9.0.0, <= 9.0.20, ECOSYSTEM:introduced=9.0.0,fixed=9.0.21; Microsoft.NetCore.App.Runtime.linux-arm64 (NuGet) >= 9.0.0, <= 9.0.20, ECOSYSTEM:introduced=9.0.0,fixed=9.0.21; Microsoft.NetCore.App.Runtime.linux-musl-arm (NuGet) >= 9.0.0, <= 9.0.20, ECOSYSTEM:introduced=9.0.0,fixed=9.0.21; and 8 more.
Is there a fix for CVE-2026-69651?
Yes. Microsoft.NetCore.App.Runtime.linux-arm (NuGet): upgrade to 9.0.21 or later; Microsoft.NetCore.App.Runtime.linux-arm64 (NuGet): upgrade to 9.0.21 or later; Microsoft.NetCore.App.Runtime.linux-musl-arm (NuGet): upgrade to 9.0.21 or later; Microsoft.NetCore.App.Runtime.linux-musl-arm64 (NuGet): upgrade to 9.0.21 or later; Microsoft.NetCore.App.Runtime.linux-musl-x64 (NuGet): upgrade to 9.0.21 or later; Microsoft.NetCore.App.Runtime.linux-x64 (NuGet): upgrade to 9.0.21 or later; Microsoft.NetCore.App.Runtime.osx-arm64 (NuGet): upgrade to 9.0.21 or later; Microsoft.NetCore.App.Runtime.osx-x64 (NuGet): upgrade to 9.0.21 or later; Microsoft.NetCore.App.Runtime.win-arm64 (NuGet): upgrade to 9.0.21 or later; Microsoft.NetCore.App.Runtime.win-x64 (NuGet): upgrade to 9.0.21 or later; Microsoft.NetCore.App.Runtime.win-x86 (NuGet): upgrade to 9.0.21 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-69651 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-69651?
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 9.0.21 or later
    dotnet add package Microsoft.NetCore.App.Runtime.linux-arm --version 9.0.21
  • Microsoft.NetCore.App.Runtime.linux-arm64 (NuGet): upgrade to 9.0.21 or later
    dotnet add package Microsoft.NetCore.App.Runtime.linux-arm64 --version 9.0.21
  • Microsoft.NetCore.App.Runtime.linux-musl-arm (NuGet): upgrade to 9.0.21 or later
    dotnet add package Microsoft.NetCore.App.Runtime.linux-musl-arm --version 9.0.21
  • Microsoft.NetCore.App.Runtime.linux-musl-arm64 (NuGet): upgrade to 9.0.21 or later
    dotnet add package Microsoft.NetCore.App.Runtime.linux-musl-arm64 --version 9.0.21
  • Microsoft.NetCore.App.Runtime.linux-musl-x64 (NuGet): upgrade to 9.0.21 or later
    dotnet add package Microsoft.NetCore.App.Runtime.linux-musl-x64 --version 9.0.21
  • Microsoft.NetCore.App.Runtime.linux-x64 (NuGet): upgrade to 9.0.21 or later
    dotnet add package Microsoft.NetCore.App.Runtime.linux-x64 --version 9.0.21
  • Microsoft.NetCore.App.Runtime.osx-arm64 (NuGet): upgrade to 9.0.21 or later
    dotnet add package Microsoft.NetCore.App.Runtime.osx-arm64 --version 9.0.21
  • Microsoft.NetCore.App.Runtime.osx-x64 (NuGet): upgrade to 9.0.21 or later
    dotnet add package Microsoft.NetCore.App.Runtime.osx-x64 --version 9.0.21
  • Microsoft.NetCore.App.Runtime.win-arm64 (NuGet): upgrade to 9.0.21 or later
    dotnet add package Microsoft.NetCore.App.Runtime.win-arm64 --version 9.0.21
  • Microsoft.NetCore.App.Runtime.win-x64 (NuGet): upgrade to 9.0.21 or later
    dotnet add package Microsoft.NetCore.App.Runtime.win-x64 --version 9.0.21
  • Microsoft.NetCore.App.Runtime.win-x86 (NuGet): upgrade to 9.0.21 or later
    dotnet add package Microsoft.NetCore.App.Runtime.win-x86 --version 9.0.21

Technical details

The vulnerability is an algorithmic complexity issue (CWE-407) in System.Security.Cryptography.Xml and System.Private.Xml that fails to enforce proper input depth and operation-count limits during signed XML processing. An attacker can exploit this by sending malformed XML with deeply nested structures or expensive canonicalization operations over the network without authentication. The fix adds input-depth limits, operation-count bounds, DTD processing restrictions, entity validation, encrypted-data bounds, and C14N transform attribute/namespace caps.

Affected products

  • Microsoft .NET 8.0.0–8.0.31, 9.0.0–9.0.20, 10.0.0–10.0.12, 11.0.0-preview.1–11.0.0-rc.1

Identifiers

  • CVE-2026-69651
  • GHSA-3rxq-g8rj-r2cf

Timeline

  • 2026-10-13: disclosed

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