🛡️ CVE-2025-55315 — asp.net-core

🔴 CVSS 9.9 — Critical ✅ No Known Exploit CWE-444 NVD
9.9
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Microsoft Security Advisory CVE-2025-55315: .NET Security Feature Bypass Vulnerability

# Microsoft Security Advisory CVE-2025-55315: .NET Security Feature Bypass Vulnerability

<a name="executive-summary"></a>Executive summary

Microsoft is releasing this security advisory to provide information about a vulnerability in ASP.NET Core 10.0 , ASP.NET Core 9.0 , ASP.NET Core 8.0, and ASP.NET Core 2.3. This advisory also provides guidance on what developers can do to update their applications to address this vulnerability.

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.

Discussion

Discussion for this issue can be found at https://github.com/dotnet/announcements/issues/371

<a name="mitigation-factors"></a>Mitigation factors

Microsoft has not identified any mitigating factors for this vulnerability.

<a name="affected-software"></a>Affected software

  • Any ASP.NET Core 10.0 application running on ASP.NET Core 10.0.0-rc.1.25451.107 or earlier.
  • Any ASP.NET Core 9.0 application running on ASP.NET Core 9.0.9 or earlier.
  • Any ASP.NET Core application running on ASP.NET Core 8.0.20 or earlier.
  • Any ASP.NET Core 2.x application consuming the package Microsoft.AspNetCore.Server.Kestrel.Core version 2.3.0 or earlier.

<a name="affected-packages"></a>Affected Packages

The vulnerability affects any Microsoft .NET Core project if it uses any of affected packages versions listed below

Package name | Affected version | Patched version

------------ | ---------------- | -------------------------

[Microsoft.AspNetCore.Server.Kestrel.Core](https://www.nuget.org/packages/Microsoft.AspNetCore.Server.Kestrel.Core) | <= 2.3.0 | 2.3.6

<a name="ASP.NET Core 10"></a>ASP.NET Core 10

Package name | Affected version | Patched version

------------ | ---------------- | -------------------------

[Microsoft.AspNetCore.App.Runtime.linux-arm](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-arm) | 10.0.0-rc.1.25451.107 | 10.0.0-rc.2.25502.107

[Microsoft.AspNetCore.App.Runtime.linux-arm64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-arm64) | 10.0.0-rc.1.25451.107 | 10.0.0-rc.2.25502.107

[Microsoft.AspNetCore.App.Runtime.linux-musl-arm](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-musl-arm) | 10.0.0-rc.1.25451.107 | 10.0.0-rc.2.25502.107

[Microsoft.AspNetCore.App.Runtime.linux-musl-arm64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-musl-arm64) | 10.0.0-rc.1.25451.107 | 10.0.0-rc.2.25502.107

[Microsoft.AspNetCore.App.Runtime.linux-musl-x64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-musl-x64) | 10.0.0-rc.1.25451.107 | 10.0.0-rc.2.25502.107

[Microsoft.AspNetCore.App.Runtime.linux-x64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-x64) | 10.0.0-rc.1.25451.107 | 10.0.0-rc.2.25502.107

[Microsoft.AspNetCore.App.Runtime.osx-arm64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.osx-arm64) | 10.0.0-rc.1.25451.107 | 10.0.0-rc.2.25502.107

[Microsoft.AspNetCore.App.Runtime.osx-x64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.osx-x64) | 10.0.0-rc.1.25451.107 | 10.0.0-rc.2.25502.107

[Microsoft.AspNetCore.App.Runtime.win-arm](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.win-arm) | 10.0.0-rc.1.25451.107 | 10.0.0-rc.2.25502.107

[Microsoft.AspNetCore.App.Runtime.win-arm64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.win-arm64) | 10.0.0-rc.1.25451.107 | 10.0.0-rc.2.25502.107

[Microsoft.AspNetCore.App.Runtime.win-x64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.win-x64) | 10.0.0-rc.1.25451.107 | 10.0.0-rc.2.25502.107

[Microsoft.AspNetCore.App.Runtime.win-x86](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.win-x86) | 10.0.0-rc.1.25451.107 | 10.0.0-rc.2.25502.107

<a name="ASP.NET Core 9"></a>ASP.NET Core 9

Package name | Affected version | Patched version

------------ | ---------------- | -------------------------

[Microsoft.AspNetCore.App.Runtime.linux-arm](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-arm) | >= 9.0.0, <= 9.0.9 | 9.0.10

[Microsoft.AspNetCore.App.Runtime.linux-arm64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-arm64) | >= 9.0.0, <= 9.0.9 | 9.0.10

[Microsoft.AspNetCore.App.Runtime.linux-musl-arm](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-musl-arm) | >= 9.0.0, <= 9.0.9 | 9.0.10

[Microsoft.AspNetCore.App.Runtime.linux-musl-arm64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-musl-arm64) | >= 9.0.0, <= 9.0.9 | 9.0.10

[Microsoft.AspNetCore.App.Runtime.linux-musl-x64](https

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs low-level privileges on the target. No user interaction is required. The scope is changed, meaning a successful attack can affect components beyond the vulnerable one. Rated impact: confidentiality high, integrity high, availability low.

Weakness class

CVE-2025-55315 is classified as CWE-444: HTTP Request Smuggling. A proxy and a server disagree on where one request ends, letting an attacker slip a second request past the front end.

Affected software

CVE-2025-55315 is recorded against 16 packages.

  • asp.net-core (from 9.0.0 up to 9.0.10)
  • aspnet-core
  • microsoft.aspnetcore.app.runtime.linux-arm (from 8.0.0 up to 8.0.21)
  • microsoft.aspnetcore.app.runtime.linux-arm64 (from 8.0.0 up to 8.0.21)
  • microsoft.aspnetcore.app.runtime.linux-musl-arm (from 8.0.0 up to 8.0.21)
  • microsoft.aspnetcore.app.runtime.linux-musl-arm64 (from 8.0.0 up to 8.0.21)
  • microsoft.aspnetcore.app.runtime.linux-musl-x64 (from 8.0.0 up to 8.0.21)
  • microsoft.aspnetcore.app.runtime.linux-x64 (from 8.0.0 up to 8.0.21)
  • microsoft.aspnetcore.app.runtime.osx-arm64 (from 8.0.0 up to 8.0.21)
  • microsoft.aspnetcore.app.runtime.osx-x64 (from 8.0.0 up to 8.0.21)
  • microsoft.aspnetcore.app.runtime.win-arm (from 8.0.0 up to 8.0.21)
  • microsoft.aspnetcore.app.runtime.win-arm64 (from 8.0.0 up to 8.0.21)
  • microsoft.aspnetcore.app.runtime.win-x64 (from 8.0.0 up to 8.0.21)
  • microsoft.aspnetcore.app.runtime.win-x86 (from 8.0.0 up to 8.0.21)
  • microsoft.aspnetcore.server.kestrel.core (fixed in 2.3.6)
  • visual-studio-2022 (from 17.14.0 up to 17.14.17)

Timeline and source

Published on 14 October 2025 and last revised on 17 June 2026. No public exploit is currently recorded for this entry. Record sourced from NVD.

References

msrc.microsoft.com
andrewlock.net
gist.github.com

CVE-2025-55315 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity CRITICAL
CVSS Score 9.9
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:L
CWE CWE-444
Public Exploit ✅ No
Source NVD
Published 2025-10-14
Updated 2026-08-12
Modified 2026-06-17
Fix URL N/A

Affected Packages

Software From version Fixed in
asp.net-core 9.0.0 9.0.10
aspnet-core — —
microsoft.aspnetcore.app.runtime.linux-arm 8.0.0 8.0.21
microsoft.aspnetcore.app.runtime.linux-arm64 8.0.0 8.0.21
microsoft.aspnetcore.app.runtime.linux-musl-arm 8.0.0 8.0.21
microsoft.aspnetcore.app.runtime.linux-musl-arm64 8.0.0 8.0.21
microsoft.aspnetcore.app.runtime.linux-musl-x64 8.0.0 8.0.21
microsoft.aspnetcore.app.runtime.linux-x64 8.0.0 8.0.21
microsoft.aspnetcore.app.runtime.osx-arm64 8.0.0 8.0.21
microsoft.aspnetcore.app.runtime.osx-x64 8.0.0 8.0.21
microsoft.aspnetcore.app.runtime.win-arm 8.0.0 8.0.21
microsoft.aspnetcore.app.runtime.win-arm64 8.0.0 8.0.21
microsoft.aspnetcore.app.runtime.win-x64 8.0.0 8.0.21
microsoft.aspnetcore.app.runtime.win-x86 8.0.0 8.0.21
microsoft.aspnetcore.server.kestrel.core — 2.3.6
visual-studio-2022 17.14.0 17.14.17

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