CVE-2026-47300: Microsoft ASP.NET Core privilege escalation in authentication algorithm

CVE-2026-47300 · Severity: high · CVSS 8.8 · Published 2026-07-14

A security vulnerability exists in the ASP.NET Core Negotiate authentication component, which is used by web applications to handle Windows-based logins. If an application also uses LDAP to retrieve user roles, an attacker could exploit this flaw to gain higher-level permissions than they should have. This could allow an unauthorized user to access sensitive data or perform administrative actions within the affected application.

Technologies: Microsoft Visual Studio 2022, Microsoft.AspNetCore.Authentication.Negotiate (NuGet). Vendors: Microsoft, NuGet.

Quick answers

Is CVE-2026-47300 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-47300 being exploited in the wild.
How severe is CVE-2026-47300?
High severity, with a CVSS score of 8.8, published 14 July 2026.
Which products and versions are affected?
Microsoft AspNetCore.Authentication.Negotiate >= 8.0.0, <= 8.0.28; >= 9.0.0, <= 9.0.17; >= 10.0.0, <= 10.0.9; Microsoft Visual Studio 2022 17.12 to < 17.12.22, 17.14 to < 17.14.36; Microsoft.AspNetCore.Authentication.Negotiate (NuGet) ECOSYSTEM:introduced=10.0.0,fixed=10.0.10.
Is there a fix for CVE-2026-47300?
Yes. Microsoft.AspNetCore.Authentication.Negotiate (NuGet): upgrade to 10.0.10 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-47300 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-47300?
Check whether you run Microsoft AspNetCore.Authentication.Negotiate, Microsoft Visual Studio 2022 or Microsoft.AspNetCore.Authentication.Negotiate (NuGet) 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.AspNetCore.Authentication.Negotiate (NuGet): upgrade to 10.0.10 or later
    dotnet add package Microsoft.AspNetCore.Authentication.Negotiate --version 10.0.10

Technical details

An elevation of privilege vulnerability exists in the Microsoft.AspNetCore.Authentication.Negotiate package due to an incorrect implementation of the authentication algorithm (CWE-303). The root cause is improper validation within the Negotiate authentication handler when the application is configured to use LDAP to retrieve role information. An authenticated attacker can exploit this over the network with low complexity to elevate their privileges. The vulnerability affects .NET 8, 9, and 10. Microsoft has released patched versions (8.0.29, 9.0.18, and 10.0.10) to address this issue.

Affected products

  • Microsoft Microsoft.AspNetCore.Authentication.Negotiate >= 8.0.0, <= 8.0.28; >= 9.0.0, <= 9.0.17; >= 10.0.0, <= 10.0.9

Identifiers

  • CVE-2026-47300
  • GHSA-8prm-248r-h957

Timeline

  • 2026-07-14: disclosed: Initial advisory publication
  • 2026-07-14: patched: Patched versions released for .NET 8, 9, and 10
  • 2026-07-21: advisory: GitHub Advisory reviewed and updated

References

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