Microsoft Security Advisory CVE-2026-32178 – .NET Spoofing Vulnerability
Date: 2026-04
Affected: nuget/Microsoft.NetCore.App.Runtime.win-x86, nuget/Microsoft.NetCore.App.Runtime.win-x64, nuget/Microsoft.NetCore.App.Runtime.win-arm64
Attack vector: other
Category: vulnerability-disclosure
Severity: Low
CVE: CVE-2026-32178
CWE: CWE-138
CVSS:  (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:N)

## Executive Summary: Microsoft is releasing this security advisory to provide information about a vulnerability in .NET 8.0, .NET 9.0, and .NET 10.0. This advisory also provides guidance on what developers can do to update their applications to remove this vulnerability. A vulnerability exists in System.Net.Mail where specially crafted data allows an unauthorized attacker to perform a spoofing attack over the network. ## Announcement Announcement for this issue can be found at https://github.com/dotnet/announcements/issues/12345 ## CVSS Details - **Version:** 3.1 - **Severity:** High - **Score:** 7.5 - **Vector:** 7.5: AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N/E:U/RL:O/RC:C - **Weakness:** CWE-138: Improper Neutralization of Special Elements ## Affected Platforms - **Platforms:** All - **Architectures:** All ## <a name="affected-packages"></a>Affected Packages The vulnerability affects any Microsoft .NET project if it uses any of affected package versions listed below ### <a name=".NET 8"></a>.NET 8 Package name | Affected version | Patched version ------------ | ---------------- | ------------------------- [Microsoft.NetCore.App.Runtime.linux-arm](https://www.nuget.org/packages/Microsoft.NetCore.App.Runtime.linux-arm) | >= 8.0.0, <= 8.0.25 | 8.0.26 [Microsoft.NetCore.App.Runtime.linux-arm64](https://www.nuget.org/packages/Microsoft.NetCore.App.Runtime.linux-arm64) | >= 8.0.0, <= 8.0.25 | 8.0.26 [Microsoft.NetCore.App.Runtime.linux-musl-arm](htt


Mitigations:

Architectural layers (MAESTRO):