CVE-2026-47303: Microsoft ASP.NET Core authentication bypass and privilege escalation

CVE-2026-47303 · Severity: high · CVSS 8.8 · Published 2026-07-14

A security vulnerability exists in the ASP.NET Core component responsible for handling Windows-based authentication (Negotiate). An attacker with basic network access could exploit this flaw to gain higher-level permissions than they should have, potentially leading to unauthorized access to sensitive data or administrative functions. Organizations using .NET 8, 9, or 10 should update their applications to the latest patched versions to prevent unauthorized privilege escalation.

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

Quick answers

Is CVE-2026-47303 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-47303 being exploited in the wild.
How severe is CVE-2026-47303?
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 17.12.0 to 17.12.21; Microsoft.AspNetCore.Authentication.Negotiate (NuGet) ECOSYSTEM:introduced=10.0.0,fixed=10.0.10.
Is there a fix for CVE-2026-47303?
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-2026-47303 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-47303?
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 improper parsing of authentication data. The flaw involves a combination of LDAP injection (CWE-90), authentication bypass via assumed-immutable data (CWE-302), and incorrect authorization (CWE-863). A remote attacker with low privileges can exploit this over the network without user interaction to bypass security checks or escalate their authority within the application. The vulnerability is addressed in versions 8.0.29, 9.0.18, and 10.0.10. Developers must update their NuGet package references and redeploy applications, including self-contained deployments.

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-2026-47303
  • GHSA-2p3q-h3hg-jcqq

Timeline

  • 2026-07-14: disclosed: Initial advisory publication
  • 2026-07-21: advisory: GitHub Advisory updated

References

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