CVE-2026-114156

Improper input validation in ASP.NET Core allows an unauthorized attacker to bypass a security feature over a network.

Improper input validation in ASP.NET Core allows an unauthorized attacker to bypass a security feature over a network.

Executive summary

Microsoft is releasing this security advisory to provide information about a vulnerability in ASP.NET Core. This advisory provides guidance on updating affected applications and components.

PathString.StartsWithSegments can mishandle percent-encoded backslashes and permit authorization checks to match an unintended path.

Announcement

Announcement for this issue can be found at https://github.com/dotnet/announcements/issues/510

CVSS Details

• Version: 3.1
• Severity: Medium
• Score: 6.5 (base score)
• Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N/E:U/RL:O/RC:C
• Weakness: CWE-41

Affected Platforms

• Platforms: Windows, Linux, macOS
• Architectures: All

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

The tables list affected version ranges and fixed package versions. Runtime and standalone deliveries are listed separately.

.NET 11.0 - affected runtime packages

Package | Affected version | Patched version --- | --- | --- Microsoft.AspNetCore.App.Runtime.linux-arm | >= 11.0.0-preview.7.26381.103, <= 11.0.0-rc.3.26522.148 | 11.0.0 Microsoft.AspNetCore.App.Runtime.linux-arm64 | >= 11.0.0-preview.7.26381.103, <= 11.0.0-rc.3.26522.148 | 11.0.0 Microsoft.AspNetCore.App.Runtime.linux-musl-arm | >= 11.0.0-preview.7.26381.103, <= 11.0.0-rc.3.26522.148 | 11.0.0 Microsoft.AspNetCore.App.Runtime.linux-musl-arm64 | >= 11.0.0-preview.7.26381.103, <= 11.0.0-rc.3.26522.148 | 11.0.0 Microsoft.AspNetCore.App.Runtime.linux-musl-x64 | >= 11.0.0-preview.7.26381.103, <= 11.0.0-rc.3.26522.148 | 11.0.0 Microsoft.AspNetCore.App.Runtime.linux-x64 | >= 11.0.0-preview.7.26381.103, <= 11.0.0-rc.3.26522.148 | 11.0.0 Microsoft.AspNetCore.App.Runtime.osx-arm64 | >= 11.0.0-preview.7.26381.103, <= 11.0.0-rc.3.26522.148 | 11.0.0 Microsoft.AspNetCore.App.Runtime.osx-x64 | >= 11.0.0-preview.7.26381.103, <= 11.0.0-rc.3.26522.148 | 11.0.0 Microsoft.AspNetCore.App.Runtime.win-arm64 | >= 11.0.0-preview.7.26381.103, <= 11.0.0-rc.3.26522.148 | 11.0.0 Microsoft.AspNetCore.App.Runtime.win-x64 | >= 11.0.0-preview.7.26381.103, <= 11.0.0-rc.3.26522.148 | 11.0.0 Microsoft.AspNetCore.App.Runtime.win-x86 | >= 11.0.0-preview.7.26381.103, <= 11.0.0-rc.3.26522.148 | 11.0.0

Advisory FAQ

<a name="how-affected"></a>How do I know if I am affected?

Check the deployed runtime and application package versions against the affected ranges above. Self-contained applications include their own runtime; updating a machine-wide runtime does not replace it.

<a name="how-fix"></a>How do I fix the issue?

Install the applicable runtime or update each independently referenced package to the fixed version above. Restart applications. Rebuild and redeploy self-contained applications; updating a machine-wide runtime does not replace their embedded runtime. An SDK update alone does not update an application's standalone package references.

Other Information

Reporting Security Issues

If you have found a potential security issue in a supported version of .NET, please report it to the Microsoft Security Response Center (MSRC) via the [MSRC Researcher…

Duplicate Advisory

This advisory has been withdrawn because it is a duplicate of GHSA-8w29-6cjc-h6w4. This link is maintained to preserve external references.

Original Description

Improper input validation in ASP.NET Core allows an unauthorized attacker to bypass a security feature over a network.

Improper input validation in ASP.NET Core allows an unauthorized attacker to bypass a security feature over a network.

Executive summary

Microsoft is releasing this security advisory to provide information about a vulnerability in ASP.NET Core. This advisory provides guidance on updating affected applications and components.

PathString.StartsWithSegments can mishandle percent-encoded backslashes and permit authorization checks to match an unintended path.

Announcement

Announcement for this issue can be found at https://github.com/dotnet/announcements/issues/510

CVSS Details

• Version: 3.1
• Severity: Medium
• Score: 6.5 (base score)
• Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N/E:U/RL:O/RC:C
• Weakness: CWE-41

Affected Platforms

• Platforms: Windows, Linux, macOS
• Architectures: All

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

The tables list affected version ranges and fixed package versions. Runtime and standalone deliveries are listed separately.

.NET 11.0 - affected runtime packages

Package | Affected version | Patched version --- | --- | --- Microsoft.AspNetCore.App.Runtime.linux-arm | >= 11.0.0-preview.7.26381.103, <= 11.0.0-rc.3.26522.148 | 11.0.0 Microsoft.AspNetCore.App.Runtime.linux-arm64 | >= 11.0.0-preview.7.26381.103, <= 11.0.0-rc.3.26522.148 | 11.0.0 Microsoft.AspNetCore.App.Runtime.linux-musl-arm | >= 11.0.0-preview.7.26381.103, <= 11.0.0-rc.3.26522.148 | 11.0.0 Microsoft.AspNetCore.App.Runtime.linux-musl-arm64 | >= 11.0.0-preview.7.26381.103, <= 11.0.0-rc.3.26522.148 | 11.0.0 Microsoft.AspNetCore.App.Runtime.linux-musl-x64 | >= 11.0.0-preview.7.26381.103, <= 11.0.0-rc.3.26522.148 | 11.0.0 Microsoft.AspNetCore.App.Runtime.linux-x64 | >= 11.0.0-preview.7.26381.103, <= 11.0.0-rc.3.26522.148 | 11.0.0 Microsoft.AspNetCore.App.Runtime.osx-arm64 | >= 11.0.0-preview.7.26381.103, <= 11.0.0-rc.3.26522.148 | 11.0.0 Microsoft.AspNetCore.App.Runtime.osx-x64 | >= 11.0.0-preview.7.26381.103, <= 11.0.0-rc.3.26522.148 | 11.0.0 Microsoft.AspNetCore.App.Runtime.win-arm64 | >= 11.0.0-preview.7.26381.103, <= 11.0.0-rc.3.26522.148 | 11.0.0 Microsoft.AspNetCore.App.Runtime.win-x64 | >= 11.0.0-preview.7.26381.103, <= 11.0.0-rc.3.26522.148 | 11.0.0 Microsoft.AspNetCore.App.Runtime.win-x86 | >= 11.0.0-preview.7.26381.103, <= 11.0.0-rc.3.26522.148 | 11.0.0

Advisory FAQ

<a name="how-affected"></a>How do I know if I am affected?

Check the deployed runtime and application package versions against the affected ranges above. Self-contained applications include their own runtime; updating a machine-wide runtime does not replace it.

<a name="how-fix"></a>How do I fix the issue?

Install the applicable runtime or update each independently referenced package to the fixed version above. Restart applications. Rebuild and redeploy self-contained applications; updating a machine-wide runtime does not replace their embedded runtime. An SDK update alone does not update an application's standalone package references.

Other Information

Reporting Security Issues

If you have found a potential security issue in a supported version of .NET, please report it to the Microsoft Security Response Center (MSRC) via the [MSRC Researcher…

Duplicate Advisory

This advisory has been withdrawn because it is a duplicate of GHSA-8w29-6cjc-h6w4. This link is maintained to preserve external references.

Original Description

Improper input validation in ASP.NET Core allows an unauthorized attacker to bypass a security feature over a network.