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Asp.net CoreApplication · Microsoft

CVE-2025-55315

CRITICAL · 9.9 CVSS v3.1 Published 2025-10-14
Fix available
A fix is available. Upgrade to 2.3.6 / 8.0.21 or later.
See remediation →
100/100
Remediation priority · Urgent
High EPSS Remotely reachable 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
Inconsistent interpretation of http requests ('http request/response smuggling') in ASP.NET Core allows an authorized attacker to bypass a security feature 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

ASP.NET Core contains an HTTP request smuggling vulnerability where inconsistent interpretation of HTTP requests allows an authorized attacker to bypass a security feature. This occurs when the ASP.NET Core server parses HTTP requests differently than upstream proxies or other components in the request chain, enabling request smuggling attacks.

MitigationApply the official Microsoft ASP.NET Core security updates for CVE-2025-55315 and review Kestrel and any reverse proxy configurations for HTTP parsing inconsistencies.

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:>= 2.3.0, < 2.3.6>= 8.0.0, < 8.0.21>= 9.0.0, < 9.0.10
Visual Studio 2022Application
Affected:>= 17.10.0, < 17.10.20>= 17.12.10, < 17.12.13>= 17.14.0, < 17.14.17

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
Low
User interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
Low

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

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. Check installed ASP.NET Core runtime version
    Run 'dotnet --list-runtimes' to see installed runtime versions. Look for entries starting with 'Microsoft.AspNetCore.App' and note the version number.
    Affected if The runtime version falls within any of these ranges: 2.3.0 to 2.3.5, 8.0.0 to 8.0.20, or 9.0.0 to 9.0.9
  2. Check ASP.NET Core SDK version
    Run 'dotnet --list-sdks' to see installed SDK versions. Note the version numbers for any SDKs matching the affected version patterns.
    Affected if The SDK version matches the same ranges as the runtime (2.3.x, 8.0.x before 8.0.21, 9.0.x before 9.0.10)
  3. Determine if application listens on network
    Review application configuration files (appsettings.json, Program.cs, or deployment manifests) to verify if the Kestrel or HTTP.sys server is bound to a network interface (0.0.0.0 or specific IP) rather than localhost only.
    Affected if The application is configured to accept HTTP requests over a network interface (not localhost-only)
  4. Check Visual Studio 2022 installation if applicable
    Open Visual Studio Installer, click Modify on the VS2022 installation, and note the version shown in the title bar or go to Help > About Microsoft Visual Studio.
    Affected if Visual Studio 2022 version is 17.10.x before 17.10.20, 17.12.x before 17.12.13, or 17.14.x before 17.14.17

You are affected if you run any ASP.NET Core runtime or SDK version 2.3.0-2.3.5, 8.0.0-8.0.20, or 9.0.0-9.0.9 that accepts network requests, or use vulnerable Visual Studio 2022 versions for development.

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 2.3.6 / 8.0.21 / 9.0.10 or later
Fixed in 2.3.68.0.219.0.10
Interim mitigation

Apply the official Microsoft ASP.NET Core security updates for CVE-2025-55315 and review Kestrel and any reverse proxy configurations for HTTP parsing inconsistencies.

Recommended fix High confidence

ASP.NET Core 2.3.6, 8.0.21, or 9.0.10 (depending on major version); Visual Studio 2022 to 17.10.20/17.12.13/17.14.17

  1. Identify the current ASP.NET Core version in use by checking the project file (.csproj) or running `dotnet --version`
  2. For .NET 8.0.x: Upgrade to version 8.0.21 or later by updating the target framework in the project file and restoring packages
  3. For .NET 9.0.x: Upgrade to version 9.0.10 or later by updating the target framework in the project file and restoring packages
  4. For .NET Core 2.3.x: Upgrade to version 2.3.6 or later (note: .NET Core 2.3 is end-of-life, consider migrating to a supported version)
  5. If using Visual Studio 2022: Update to version 17.10.20, 17.12.13, or 17.14.17 (whichever corresponds to your current version) via Visual Studio Installer
  6. Rebuild and redeploy the application
  7. Verify the application functions correctly after the update
Caveat Minor version upgrades may include behavior changes; review release notes for any breaking changes in the target version

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

Fix this in Asp.net Core Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing6.0 h
  • Review / QA2.0 h
14.0 hours of engineering $2,380
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,808.

Scan for this in your stack

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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-2025-55315 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