CVE-2026-26131

Incorrect default permissions in .NET allows an authorized attacker to elevate privileges locally.

Incorrect default permissions in .NET allows an authorized attacker to elevate privileges locally.

Microsoft Security Advisory CVE-2026-26131 – .NET Elevation of Privilege Vulnerability

Executive summary

Microsoft is releasing this security advisory to provide information about a vulnerability in .NET 10.0. This advisory also provides guidance on what developers can do to update their applications to remove this vulnerability.

An elevation of privilege vulnerability exists in .NET due to improper authorization. Incorrect packaging permissions could allow an attacker to gain elevated privileges.

Announcement

Announcement for this issue can be found at https://github.com/dotnet/announcements/issues/386

CVSS Details

• Severity: High
• Version: 3.1
• Score: 7.8
• Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
• Weakness: CWE-276 (Incorrect Default Permissions)

Affected Platforms

• Platforms: Linux
• Architectures: All

Affected Products

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

Package name | Affected version | Patched version ------------ | ---------------- | ------------------------- Microsoft.NetCore.App.Runtime.linux-arm | >= 10.0.0, <= 10.0.3 | 10.0.4 Microsoft.NetCore.App.Runtime.linux-arm64 | >= 10.0.0, <= 10.0.3 | 10.0.4 Microsoft.NetCore.App.Runtime.linux-musl-arm | >= 10.0.0, <= 10.0.3 | 10.0.4 Microsoft.NetCore.App.Runtime.linux-musl-arm64 | >= 10.0.0, <= 10.0.3 | 10.0.4 Microsoft.NetCore.App.Runtime.linux-musl-x64 | >= 10.0.0, <= 10.0.3 | 10.0.4 Microsoft.NetCore.App.Runtime.linux-x64 | >= 10.0.0, <= 10.0.3 | 10.0.4

Advisory FAQ

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

If using an affected package listed in affected products, you're exposed to the vulnerability.

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

1. To fix the issue please install the latest version of .NET 10.0. If you have installed one or more .NET SDKs through Visual Studio, Visual Studio will prompt you to update Visual Studio, which will also update your .NET SDKs.
2. If your application references the vulnerable package, update the package reference to the patched version. You can list the versions you have installed by running the dotnet --info command.

Once you have installed the updated runtime or SDK, restart your apps for the update to take effect.

Additionally, if you've deployed self-contained applications targeting any of the impacted versions, these applications are also vulnerable and must be recompiled and redeployed.

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 Portal. Further information can be found in the MSRC Report an Issue FAQ.

Security reports made through MSRC may qualify for the Microsoft .NET Bounty. Details of the Microsoft .NET Bounty Program including terms and conditions are at https://aka.ms/corebounty.

Support

You can ask questions about this issue on GitHub in the .NET GitHub organization. The main repos are located at https://github.com/dotnet/runtime. The Announcements repo (https://github.com/dotnet/Announcements) will contain this bulletin as an issue and will include a link to a discussion issue. You can ask…

Incorrect default permissions in .NET allows an authorized attacker to elevate privileges locally.

Incorrect default permissions in .NET allows an authorized attacker to elevate privileges locally.

Microsoft Security Advisory CVE-2026-26131 – .NET Elevation of Privilege Vulnerability

Executive summary

Microsoft is releasing this security advisory to provide information about a vulnerability in .NET 10.0. This advisory also provides guidance on what developers can do to update their applications to remove this vulnerability.

An elevation of privilege vulnerability exists in .NET due to improper authorization. Incorrect packaging permissions could allow an attacker to gain elevated privileges.

Announcement

Announcement for this issue can be found at https://github.com/dotnet/announcements/issues/386

CVSS Details

• Severity: High
• Version: 3.1
• Score: 7.8
• Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
• Weakness: CWE-276 (Incorrect Default Permissions)

Affected Platforms

• Platforms: Linux
• Architectures: All

Affected Products

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

Package name | Affected version | Patched version ------------ | ---------------- | ------------------------- Microsoft.NetCore.App.Runtime.linux-arm | >= 10.0.0, <= 10.0.3 | 10.0.4 Microsoft.NetCore.App.Runtime.linux-arm64 | >= 10.0.0, <= 10.0.3 | 10.0.4 Microsoft.NetCore.App.Runtime.linux-musl-arm | >= 10.0.0, <= 10.0.3 | 10.0.4 Microsoft.NetCore.App.Runtime.linux-musl-arm64 | >= 10.0.0, <= 10.0.3 | 10.0.4 Microsoft.NetCore.App.Runtime.linux-musl-x64 | >= 10.0.0, <= 10.0.3 | 10.0.4 Microsoft.NetCore.App.Runtime.linux-x64 | >= 10.0.0, <= 10.0.3 | 10.0.4

Advisory FAQ

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

If using an affected package listed in affected products, you're exposed to the vulnerability.

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

1. To fix the issue please install the latest version of .NET 10.0. If you have installed one or more .NET SDKs through Visual Studio, Visual Studio will prompt you to update Visual Studio, which will also update your .NET SDKs.
2. If your application references the vulnerable package, update the package reference to the patched version. You can list the versions you have installed by running the dotnet --info command.

Once you have installed the updated runtime or SDK, restart your apps for the update to take effect.

Additionally, if you've deployed self-contained applications targeting any of the impacted versions, these applications are also vulnerable and must be recompiled and redeployed.

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 Portal. Further information can be found in the MSRC Report an Issue FAQ.

Security reports made through MSRC may qualify for the Microsoft .NET Bounty. Details of the Microsoft .NET Bounty Program including terms and conditions are at https://aka.ms/corebounty.

Support

You can ask questions about this issue on GitHub in the .NET GitHub organization. The main repos are located at https://github.com/dotnet/runtime. The Announcements repo (https://github.com/dotnet/Announcements) will contain this bulletin as an issue and will include a link to a discussion issue. You can ask…