CVE-2026-40372: Microsoft ASP.NET Core privilege escalation via improper signature verification

CVE-2026-40372 · Severity: critical · CVSS 9.1 · Published 2026-04-21

ASP.NET Core is a popular framework used by developers to build modern web applications and services. A security flaw in how the framework verifies digital signatures could allow an unauthorized person to gain higher-level permissions on a web server over the internet. This could lead to unauthorized access to sensitive data or the ability to perform administrative actions without proper credentials.

Technologies: Microsoft Asp.Net Core, Microsoft Visual Studio 2026. Vendors: Microsoft, NuGet.

Quick answers

Is CVE-2026-40372 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-40372 being exploited in the wild.
How severe is CVE-2026-40372?
Critical severity, with a CVSS score of 9.1, published 21 April 2026.
Which products and versions are affected?
Microsoft Asp.Net Core 10.0.0 to 10.0.6; Microsoft Visual Studio 2026 18.5.0 to 18.5.1; Microsoft.AspNetCore.DataProtection (NuGet) >= 10.0.0, <= 10.0.6, ECOSYSTEM:introduced=10.0.0,fixed=10.0.7.
Is there a fix for CVE-2026-40372?
Yes. Microsoft.AspNetCore.DataProtection (NuGet): upgrade to 10.0.7 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-40372 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-40372?
Check whether you run Microsoft Asp.Net Core, Microsoft Visual Studio 2026 or Microsoft.AspNetCore.DataProtection (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.DataProtection (NuGet): upgrade to 10.0.7 or later
    dotnet add package Microsoft.AspNetCore.DataProtection --version 10.0.7

Technical details

A privilege escalation vulnerability exists in ASP.NET Core due to improper verification of cryptographic signatures (CWE-347). The flaw allows a remote, unauthenticated attacker to bypass security checks by providing a specially crafted signature that the system incorrectly validates. Successful exploitation enables the attacker to gain elevated privileges within the context of the application. The vulnerability affects ASP.NET Core 10.0 (versions prior to 10.0.7) and Visual Studio 2026 version 18.5 (versions prior to 18.5.2). Microsoft has released security updates to address this issue.

Affected products

  • Microsoft ASP.NET Core 10.0 10.0.0 to 10.0.6
  • Microsoft Visual Studio 2026 version 18.5 18.5.0 to 18.5.1

Identifiers

  • CVE-2026-40372
  • GHSA-9mv3-2cwr-p262

Timeline

  • 2026-04-21: disclosed: Initial disclosure by Microsoft and Red Hat
  • 2026-04-21: advisory: NVD published the CVE record
  • 2026-06-27: other: Last modified date in NVD record

References

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