Microsoft Security Advisory CVE-2025-55248: .NET Information Disclosure Vulnerability
Date: 2025-10
Affected: nuget/Microsoft.NetCore.App.Runtime.win-x86, nuget/Microsoft.NetCore.App.Runtime.win-x64, nuget/Microsoft.NetCore.App.Runtime.win-arm64
Attack vector: info-disclosure
Category: vulnerability-disclosure
Severity: Medium
CVE: CVE-2025-55248
CWE: CWE-326
CVSS: 5.7 (CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:N/A:N)

# 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/Mic


Mitigations:

Architectural layers (MAESTRO):