GitHub Security Advisory: GHSA-gwq6-fmvp-qp68
Package: Microsoft.NetCore.App.Runtime.linux-musl-arm (NUGET)
Severity: MODERATE (CVSS 5.7)
CWE: CWE-326: Inadequate Encryption Strength
Vulnerable versions: >= 8.0.0, <= 8.0.20
Patched in: 8.0.21

Summary: Microsoft Security Advisory CVE-2025-55248: .NET Information Disclosure Vulnerability

Details:
# Microsoft Security Advisory CVE-2025-55248 | .NET Information Disclosure Vulnerability

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

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

A MITM (man in the middle) attacker may prevent use of TLS between client and SMTP server, forcing client to send data over unencrypted connection.

## Announcement

Announcement for this issue can be found at https://github.com/dotnet/announcements/issues/372

## <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 .NET 8.0 application running on .NET 8.0.20 or earlier.
* Any .NET 9.0 application running on .NET 9.0.9 or earlier.

## <a name="affected-packages"></a>Affected Packages
The vulnerability affects any Microsoft .NET project if it uses any of affected packages versions listed below

### <a name=".NET 9"></a>.NET 9
Package name | Affected version | Patched version
------------ | ---------------- | -------------------------
[Microsoft.NetCore.App.Runtime.linux-arm](https://www.nuget.org/packages/Microsoft.NetCore.App.Runtime.linux-arm)               | >= 9.0.0, < =9.0.9 | 9.0.10
[Microsoft.NetCore.App.Runtime.linux-arm64](https://www.nuget.org/packages/Microsoft.NetCore.App.Runtime.linux-arm64)           | >= 9.0.0, <= 9.0.9 | 9.0.10
[Microsoft.NetCore.App.Runtime.linux-musl-arm](https://www.nuget.org/packages/Microsoft.NetCore.App.Runtime.linux-musl-arm)     | >= 9.0.0, <= 9.0.9 | 9.0.10
[Microsoft.NetCore.App.Runtime.linux-musl-arm64](https://www.nuget.org/packages/Microsoft.NetCore.App.Runtime.linux-musl-arm64) | >= 9.0.0, <= 9.0.9 | 9.0.10
[Microsoft.NetCore.App.Runtime.linux-musl-x64](https://www.nuget.org/packages/Microsoft.NetCore.App.Runtime.linux-musl-x64)     | >= 9.0.0, <= 9.0.9 | 9.0.10
[Microsoft.NetCore.App.Runtime.linux-x64](https://www.nuget.org/packages/Microsoft.NetCore.App.Runtime.linux-x64)               | >= 9.0.0, <= 9.0.9 | 9.0.10
[Microsoft.NetCore.App.Runtime.osx-arm64](https://www.nuget.org/packages/Microsoft.NetCore.App.Runtime.osx-arm64)               | >= 9.0.0, <= 9.0.9 | 9.0.10
[Microsoft.NetCore.App.Runtime.osx-x64](https://www.nuget.org/packages/Microsoft.NetCore.App.Runtime.osx-x64)                   | >= 9.0.0, <= 9.0.9 | 9.0.10
[Microsoft.NetCore.App.Runtime.win-arm](https://www.nuget.org/packages/Microsoft.NetCore.App.Runtime.win-arm)                   | >= 9.0.0, <= 9.0.9 | 9.0.10
[Microsoft.NetCore.App.Runtime.win-arm64](https://www.nuget.org/packages/Microsoft.NetCore.App.Runtime.win-arm64)               | >= 9.0.0, <= 9.0.9 | 9.0.10
[Microsoft.NetCore.App.Runtime.win-x64](https://www.nuget.org/packages/Microsoft.NetCore.App.Runtime.win-x64)                   | >= 9.0.0, <= 9.0.9 | 9.0.1