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Asp.net CoreApplication · Microsoft

CVE-2026-40372

CRITICAL · 9.1 CVSS v3.1 Published 2026-04-21
Fix available
A fix is available. Upgrade to 10.0.7 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Improper verification of cryptographic signature in ASP.NET Core allows an unauthorized attacker to elevate privileges over a network.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

This vulnerability in ASP.NET Core involves improper verification of cryptographic signatures, allowing unauthenticated attackers to elevate privileges over a network. The flaw enables bypass of signature validation logic, potentially allowing attackers to forge tokens or messages that would be trusted by the application.

MitigationApply the latest ASP.NET Core security updates and patch all affected instances. Review and validate that cryptographic signature verification is correctly implemented in all authentication paths, particularly around token validation and message signing.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Asp.net CoreApplication
Affected:>= 10.0.0, < 10.0.7

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify installed ASP.NET Core runtime version
    Run 'dotnet --list-runtimes' in command prompt or check the installed runtime version via Control Panel > Programs and Features. Look for entries starting with 'Microsoft.AspNetCore.App' or 'Microsoft.WindowsDesktop.App'.
    Affected if The runtime version falls within 10.0.0 through 10.0.6 (the affected range before the patch).
  2. Identify installed ASP.NET Core SDK version
    Run 'dotnet --list-sdks' in command prompt. Note the SDK version number displayed.
    Affected if The SDK version is 10.0.0 through 10.0.106 (corresponding to unpatched releases).
  3. Locate authentication configuration in application code
    Inspect the application's startup or Program.cs file for calls to 'AddJwtBearer', 'AddCookie', 'AddOpenIdConnect', or other authentication handlers. Also check for 'services.AddAuthentication()' calls and any token validation parameters.
    Affected if JWT bearer authentication, cookie authentication, or OpenID Connect authentication is configured and uses signature validation for tokens.
  4. Check for custom token or data signing implementations
    Search codebase for classes implementing 'ISecurityTokenValidator', 'SecurityTokenHandler', or custom implementations of token creation/validation. Look for usage of 'JsonWebTokenHandler' or 'JwtSecurityTokenHandler'.
    Affected if Custom or built-in token handling code that performs cryptographic signature verification on tokens is present in the application.
  5. Review Data Protection API usage for signed data
    Inspect code for calls to 'IDataProtectionProvider' or 'IDataProtection' to protect/unprotect data. Check if 'ITicketStore' implementations are used for cookie authentication session storage.
    Affected if ASP.NET Core Data Protection API is used for signing cookies, tokens, or other data payloads that could be forged.

A system is affected if it runs any ASP.NET Core version between 10.0.0 and 10.0.6 inclusive AND utilizes authentication or data signing mechanisms that rely on cryptographic signature validation.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 10.0.7 or later
Fixed in 10.0.7
Interim mitigation

Apply the latest ASP.NET Core security updates and patch all affected instances. Review and validate that cryptographic signature verification is correctly implemented in all authentication paths, particularly around token validation and message signing.

Recommended fix High confidence

ASP.NET Core 10.0.7

  1. 1. Identify all ASP.NET Core installations in your environment running version 10.0.0 through 10.0.6.
  2. 2. Plan the upgrade during a maintenance window to minimize disruption.
  3. 3. Download and install ASP.NET Core version 10.0.7 or later from the official Microsoft download page or your package manager.
  4. 4. After upgrading, verify that all applications dependent on the .NET runtime are functioning correctly.
  5. 5. Test any authentication or authorization workflows that rely on cryptographic signature verification, as the fix addresses improper signature verification.
Caveat Review the ASP.NET Core 10.0.7 release notes for any breaking changes or behavioral differences from your current version.

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Asp.net Core Scoped from the published advisory
  • Consultation6.0 h
  • Implementation12.0 h
  • Testing10.0 h
  • Review / QA6.0 h
34.0 hours of engineering $5,940
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-40372 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data