CVE-2026-50659: .NET Spoofing Vulnerability

Published Jul 14, 2026
·
Updated

.NET Spoofing Vulnerability

Other sources

Executive summary

Microsoft is releasing this security advisory to provide information about a vulnerability in .NET SMTP client (System.Net.Mail). This advisory also provides guidance on what developers can do to update their applications to remove this vulnerability.

A spoofing vulnerability exists in the SMTP client implementation (System.Net.Mail) in .NET 8, .NET 9, and .NET 10, where an attacker can spoof messages during message routing.

Announcement

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

CVSS Details

- Version: 3.1 - Severity: Medium - Score: 6.5 - Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N - Weakness: CWE-116 (Improper Encoding or Escaping of Output)

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 10.0"></a>.NET 10.0 Package name | Affected version | Patched version ------------ | ---------------- | ------------------------- Microsoft.NetCore.App.Runtime.linux-arm | >= 10.0.0, <= 10.0.9 | 10.0.10 Microsoft.NetCore.App.Runtime.linux-arm64 | >= 10.0.0, <= 10.0.9 | 10.0.10 Microsoft.NetCore.App.Runtime.linux-musl-arm | >= 10.0.0, <= 10.0.9 | 10.0.10 Microsoft.NetCore.App.Runtime.linux-musl-arm64 | >= 10.0.0, <= 10.0.9 | 10.0.10 Microsoft.NetCore.App.Runtime.linux-musl-x64 | >= 10.0.0, <= 10.0.9 | 10.0.10 Microsoft.NetCore.App.Runtime.linux-x64 | >= 10.0.0, <= 10.0.9 | 10.0.10 Microsoft.NetCore.App.Runtime.osx-arm64 | >= 10.0.0, <= 10.0.9 | 10.0.10 Microsoft.NetCore.App.Runtime.osx-x64 | >= 10.0.0, <= 10.0.9 | 10.0.10 Microsoft.NetCore.App.Runtime.win-arm | >= 10.0.0, <= 10.0.9 | 10.0.10 Microsoft.NetCore.App.Runtime.win-arm64 | >= 10.0.0, <= 10.0.9 | 10.0.10 Microsoft.NetCore.App.Runtime.win-x64 | >= 10.0.0, <= 10.0.9 | 10.0.10 Microsoft.NetCore.App.Runtime.win-x86 | >= 10.0.0, <= 10.0.9 | 10.0.10

<a name=".NET 9.0"></a>.NET 9.0 Package name | Affected version | Patched version ------------ | ---------------- | ------------------------- Microsoft.NetCore.App.Runtime.linux-arm | >= 9.0.0, <= 9.0.17 | 9.0.18 Microsoft.NetCore.App.Runtime.linux-arm64 | >= 9.0.0, <= 9.0.17 | 9.0.18 Microsoft.NetCore.App.Runtime.linux-musl-arm | >= 9.0.0, <= 9.0.17 | 9.0.18 Microsoft.NetCore.App.Runtime.linux-musl-arm64 | >= 9.0.0, <= 9.0.17 | 9.0.18 Microsoft.NetCore.App.Runtime.linux-musl-x64 | >= 9.0.0, <= 9.0.17 | 9.0.18 Microsoft.NetCore.App.Runtime.linux-x64 | >= 9.0.0, <= 9.0.17 | 9.0.18 Microsoft.NetCore.App.Runtime.osx-arm64 | >= 9.0.0, <= 9.0.17 | 9.0.18 Microsoft.NetCore.App.Runtime.osx-x64 | >= 9.0.0, <= 9.0.17 | 9.0.18 Microsoft.NetCore.App.Runtime.win-arm | >= 9.0.0, <= 9.0.17 | 9.0.18 Microsoft.NetCore.App.Runtime.win-arm64 | >= 9.0.0, <= 9.0.17 | 9.0.18 Microsoft.NetCore.App.Runtime.win-x64 | >= 9.0.0, <= 9.0.17 | 9.0.18 Microsoft.NetCore.App.Runtime.win-x86 | >= 9.0.0, <= 9.0.17 | 9.0.18

<a name=".NET 8.0"></a>.NET 8.0 Package name | Affected version | Patched version ------------ | ---------------- | ------------------------- Microsoft.NetCore.App.Runtime.linux-arm | >= 8.0.0, <= 8.0.28 | 8.0.29 Microsoft.NetCore.App.Runtime.linux-arm64 | >= 8.0.0, <= 8.0.28 | 8.0.29 Microsoft.NetCore.App.Runtime.linux-musl-arm | >= 8.0.0, <= 8.0.28 | 8.0.29 Microsoft.NetCore.App.Runtime.linux-musl-arm64 | >= 8.0.0, <= 8.0.28 | 8.0.29 Microsoft.NetCore.App.Runtime.linux-musl-x64 | >= 8.0.0, <= 8.0.28 | 8.0.29 Microsoft.NetCore.App.Runtime.linux-x64 | >= 8.0.0, <= 8.0.28 | 8.0.29 Microsoft.NetCore.App.Runtime.osx-arm64 | >= 8.0.0, <= 8.0.28 | 8.0.29 Microsoft.NetCore.App.Runtime.osx-x64 | >= 8.0.0, <= 8.0.28 | 8.0.29 Microsoft.NetCore.App.Runtime.win-arm | >= 8.0.0, <= 8.0.28 | 8.0.29 Microsoft.NetCore.App.Runtime.win-arm64 | >= 8.0.0, <= 8.0.28 | 8.0.29 Microsoft.NetCore.App.Runtime.win-x64 | >= 8.0.0, <= 8.0.28 | 8.0.29 Microsoft.NetCore.App.Runtime.win-x86 | >= 8.0.0, <= 8.0.28 | 8.0.29

Advisory FAQ

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

If using a package listed in affected packages, 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. 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 nuget 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 questions in the linked discussion issue.

Disclaimer

The information provided in this advisory is provided "as is" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.

External Links

CVE-2026-50659

Acknowledgements

hamayanhamayan

Revisions

V1.0 (July 14, 2026): Advisory published.

— GitHub

Improper encoding or escaping of output in .NET allows an authorized attacker to perform spoofing over a network.

— Microsoft

Affected Software

133 affected componentsFixes available
Microsoft .NET 9.0 installed on Linux<9.0.18
9.0.18
Microsoft .NET 9.0 installed on Windows<9.0.18
9.0.18
Microsoft .NET 8.0 installed on Linux<8.0.29
8.0.29
Microsoft Visual Studio 2022=17.14
17.14.36
Microsoft .NET 9.0 installed on Mac OS<9.0.18
9.0.18
Microsoft Visual Studio 2022=17.12
17.12.22
Microsoft .NET 8.0 installed on Mac OS<8.0.29
8.0.29
Microsoft .NET 8.0 installed on Windows<8.0.29
8.0.29
Microsoft Visual Studio 2026=18.7
18.7.4
Microsoft .NET Framework=3.5, =4.8.1
2.0.50727.9182 & 3.0.30729.9168 & 4.8.9339.0
Microsoft .NET Framework=3.5
2.0.50727.8983 & 3.0.30729.8978
Microsoft .NET Framework=3.5
2.0.50727.8983 & 3.0.30729.8978
Microsoft .NET Framework=3.5, =4.8.1
2.0.50727.9182 & 3.0.30729.9168 & 4.8.9340.0
Microsoft .NET Framework=3.5, =4.8.1
2.0.50727.9182 & 3.0.30729.9168 & 4.8.9339.0
Microsoft .NET Framework=4.6.2, =4.7, =4.7.1, =4.7.2
4.7.4143.0
Microsoft .NET Framework=4.6.2, =4.7, =4.7.1, =4.7.2
4.7.4143.0
Microsoft .NET Framework=3.5, =4.7.2
2.0.50727.8983 & 3.0.30729.8978 & 4.7.4143.0
Microsoft .NET Framework=3.5, =4.7.2
2.0.50727.9069 & 3.0.30729.9067 & 4.7.4143.0
Microsoft .NET Framework=3.5, =4.8
2.0.50727.9182 & 3.0.30729.9168 & 4.8.4803.0
Microsoft .NET Framework=3.5, =4.8
2.0.50727.9069 & 3.0.30729.9067 & 4.8.4803.0
Microsoft .NET Framework=3.5, =4.8
2.0.50727.9182 & 3.0.30729.9168 & 4.8.4803.0
Microsoft .NET Framework=4.8
4.8.4803.0
Microsoft .NET Framework=4.8
4.8.4803.0
Microsoft .NET Framework=4.8
4.8.4803.0
Microsoft .NET Framework=3.5, =4.8.1
2.0.50727.9182 & 3.0.30729.9168
Microsoft .NET Framework=3.5, =4.8.1
2.0.50727.9182 & 3.0.30729.9168 & 4.8.9340.0
Microsoft .NET Framework=3.5, =4.8.1
2.0.50727.9182 & 3.0.30729.9168 & 4.8.9339.0
nuget/Microsoft.NetCore.App.Runtime.win-x86>=8.0.0<=8.0.28
8.0.29
nuget/Microsoft.NetCore.App.Runtime.win-x64>=8.0.0<=8.0.28
8.0.29
nuget/Microsoft.NetCore.App.Runtime.win-arm64>=8.0.0<=8.0.28
8.0.29
nuget/Microsoft.NetCore.App.Runtime.win-arm>=8.0.0<=8.0.28
8.0.29
nuget/Microsoft.NetCore.App.Runtime.osx-x64>=8.0.0<=8.0.28
8.0.29
nuget/Microsoft.NetCore.App.Runtime.osx-arm64>=8.0.0<=8.0.28
8.0.29
nuget/Microsoft.NetCore.App.Runtime.linux-x64>=8.0.0<=8.0.28
8.0.29
nuget/Microsoft.NetCore.App.Runtime.linux-musl-x64>=8.0.0<=8.0.28
8.0.29
nuget/Microsoft.NetCore.App.Runtime.linux-musl-arm64>=8.0.0<=8.0.28
8.0.29
nuget/Microsoft.NetCore.App.Runtime.linux-musl-arm>=8.0.0<=8.0.28
8.0.29
nuget/Microsoft.NetCore.App.Runtime.linux-arm64>=8.0.0<=8.0.28
8.0.29
nuget/Microsoft.NetCore.App.Runtime.linux-arm>=8.0.0<=8.0.28
8.0.29
nuget/Microsoft.NetCore.App.Runtime.win-x86>=9.0.0<=9.0.17
9.0.18
nuget/Microsoft.NetCore.App.Runtime.win-x64>=9.0.0<=9.0.17
9.0.18
nuget/Microsoft.NetCore.App.Runtime.win-arm64>=9.0.0<=9.0.17
9.0.18
nuget/Microsoft.NetCore.App.Runtime.win-arm>=9.0.0<=9.0.17
9.0.18
nuget/Microsoft.NetCore.App.Runtime.osx-x64>=9.0.0<=9.0.17
9.0.18
nuget/Microsoft.NetCore.App.Runtime.osx-arm64>=9.0.0<=9.0.17
9.0.18
nuget/Microsoft.NetCore.App.Runtime.linux-x64>=9.0.0<=9.0.17
9.0.18
nuget/Microsoft.NetCore.App.Runtime.linux-musl-x64>=9.0.0<=9.0.17
9.0.18
nuget/Microsoft.NetCore.App.Runtime.linux-musl-arm64>=9.0.0<=9.0.17
9.0.18
nuget/Microsoft.NetCore.App.Runtime.linux-musl-arm>=9.0.0<=9.0.17
9.0.18
nuget/Microsoft.NetCore.App.Runtime.linux-arm64>=9.0.0<=9.0.17
9.0.18
nuget/Microsoft.NetCore.App.Runtime.linux-arm>=9.0.0<=9.0.17
9.0.18
nuget/Microsoft.NetCore.App.Runtime.win-x86>=10.0.0<=10.0.9
10.0.10
nuget/Microsoft.NetCore.App.Runtime.win-x64>=10.0.0<=10.0.9
10.0.10
nuget/Microsoft.NetCore.App.Runtime.win-arm64>=10.0.0<=10.0.9
10.0.10
nuget/Microsoft.NetCore.App.Runtime.win-arm>=10.0.0<=10.0.9
10.0.10
nuget/Microsoft.NetCore.App.Runtime.osx-x64>=10.0.0<=10.0.9
10.0.10
nuget/Microsoft.NetCore.App.Runtime.osx-arm64>=10.0.0<=10.0.9
10.0.10
nuget/Microsoft.NetCore.App.Runtime.linux-x64>=10.0.0<=10.0.9
10.0.10
nuget/Microsoft.NetCore.App.Runtime.linux-musl-x64>=10.0.0<=10.0.9
10.0.10
nuget/Microsoft.NetCore.App.Runtime.linux-musl-arm64>=10.0.0<=10.0.9
10.0.10
nuget/Microsoft.NetCore.App.Runtime.linux-musl-arm>=10.0.0<=10.0.9
10.0.10
nuget/Microsoft.NetCore.App.Runtime.linux-arm64>=10.0.0<=10.0.9
10.0.10
nuget/Microsoft.NetCore.App.Runtime.linux-arm>=10.0.0<=10.0.9
10.0.10
Microsoft .NET Framework=4.8.1
4.8.9340.0
Microsoft .NET Framework=3.5
2.0.50727.9182 & 3.0.30729.9168
Microsoft .NET 10.0 installed on Mac OS<10.0.10
10.0.10
Microsoft .NET 10.0 installed on Linux<10.0.10
10.0.10
All of the following
Microsoft .NET Framework=4.8.1
Any of the following
Microsoft Windows 11 26h1
Microsoft Windows 11 26h1
All of the following
Microsoft .NET Framework=4.8
Any of the following
Microsoft Windows 10 1607
Microsoft Windows 10 1607
Microsoft Windows Server 2012
Microsoft Windows Server 2012=r2
Microsoft Windows Server 2016
All of the following
Any of the following
Microsoft .NET Framework=4.6.2
Microsoft .NET Framework=4.7
Microsoft .NET Framework=4.7.1
Microsoft .NET Framework=4.7.2
Any of the following
Microsoft Windows Server 2012
Microsoft Windows Server 2012=r2
All of the following
Any of the following
Microsoft .NET>=8.0.0<8.0.29
Microsoft .NET>=9.0.0<9.0.18
Any of the following
Apple macOS
Linux Linux kernel
Microsoft Windows
All of the following
Microsoft .NET>=10.0.0<10.0.6
Any of the following
Apple macOS
Linux Linux kernel
All of the following
Any of the following
Microsoft .NET Framework=3.5
Microsoft .NET Framework=4.8.1
Any of the following
Microsoft Windows 10 21h2
Microsoft Windows 10 21h2
Microsoft Windows 10 21h2
Microsoft Windows 10 22h2
Microsoft Windows 10 22h2
Microsoft Windows 10 22h2
Microsoft Windows 11 23h2
Microsoft Windows 11 23h2
Microsoft Windows 11 24h2
Microsoft Windows 11 24h2
Microsoft Windows 11 25h2
Microsoft Windows 11 25h2
Microsoft Windows Server 2022
All of the following
Any of the following
Microsoft .NET Framework=3.5
Microsoft .NET Framework=4.8
Any of the following
Microsoft Windows 10 1809
Microsoft Windows 10 1809
Microsoft Windows 10 21h2
Microsoft Windows 10 21h2
Microsoft Windows 10 21h2
Microsoft Windows 10 22h2
Microsoft Windows 10 22h2
Microsoft Windows 10 22h2
Microsoft Windows Server 2019
Microsoft Windows Server 2022
All of the following
Any of the following
Microsoft .NET Framework=3.5
Microsoft .NET Framework=4.7.2
Any of the following
Microsoft Windows 10 1607
Microsoft Windows 10 1607
Microsoft Windows 10 1809
Microsoft Windows 10 1809
Microsoft Windows Server 2016
Microsoft Windows Server 2019
All of the following
Microsoft .NET Framework=3.5
Any of the following
Microsoft Windows 11 26h1
Microsoft Windows 11 26h1
Microsoft Windows Server 2012
Microsoft Windows Server 2012=r2
Microsoft Visual Studio 2022>=17.12.0<17.12.22
Microsoft Visual Studio 2022>=17.14.0<17.14.36
Microsoft Visual Studio 2026>=18.7.0<18.7.4

Remediation

Recommended actions to resolve this vulnerability, in priority order.

  1. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 9.0.18Patch KB5104033
  2. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 8.0.29Patch KB5104032
  3. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 17.14.36
  4. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 17.12.22
  5. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 18.7.4
  6. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 2.0.50727.9182 & 3.0.30729.9168 & 4.8.9339.0Patch KB5101000
  7. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 2.0.50727.8983 & 3.0.30729.8978Patch KB5100985
  8. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 2.0.50727.8983 & 3.0.30729.8978Patch KB5100984
  9. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 2.0.50727.9182 & 3.0.30729.9168 & 4.8.9340.0Patch KB5101003
  10. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 2.0.50727.9182 & 3.0.30729.9168 & 4.8.9339.0Patch KB5101005
  11. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 4.7.4143.0Patch KB5100991
  12. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 4.7.4143.0Patch KB5100990
  13. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 2.0.50727.8983 & 3.0.30729.8978 & 4.7.4143.0Patch KB5099535
  14. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 2.0.50727.9069 & 3.0.30729.9067 & 4.7.4143.0Patch KB5100989
  15. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 2.0.50727.9182 & 3.0.30729.9168 & 4.8.4803.0Patch KB5101006
  16. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 2.0.50727.9069 & 3.0.30729.9067 & 4.8.4803.0Patch KB5101008
  17. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 2.0.50727.9182 & 3.0.30729.9168 & 4.8.4803.0Patch KB5101010
  18. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 4.8.4803.0Patch KB5101007
  19. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 4.8.4803.0Patch KB5101011
  20. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 4.8.4803.0Patch KB5101009
  21. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 2.0.50727.9182 & 3.0.30729.9168Patch KB5101014
  22. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 2.0.50727.9182 & 3.0.30729.9168 & 4.8.9339.0Patch KB5101001
  23. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 2.0.50727.9182 & 3.0.30729.9168 & 4.8.9340.0Patch KB5100998
  24. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 2.0.50727.9182 & 3.0.30729.9168 & 4.8.9339.0Patch KB5101004
  25. Upgrade

    Upgrade nuget/Microsoft.NetCore.App.Runtime.win-x86 to a version that resolves this vulnerability.

    Fixed in 8.0.29
  26. Upgrade

    Upgrade nuget/Microsoft.NetCore.App.Runtime.win-x64 to a version that resolves this vulnerability.

    Fixed in 8.0.29
  27. Upgrade

    Upgrade nuget/Microsoft.NetCore.App.Runtime.win-arm64 to a version that resolves this vulnerability.

    Fixed in 8.0.29
  28. Upgrade

    Upgrade nuget/Microsoft.NetCore.App.Runtime.win-arm to a version that resolves this vulnerability.

    Fixed in 8.0.29
  29. Upgrade

    Upgrade nuget/Microsoft.NetCore.App.Runtime.osx-x64 to a version that resolves this vulnerability.

    Fixed in 8.0.29
  30. Upgrade

    Upgrade nuget/Microsoft.NetCore.App.Runtime.osx-arm64 to a version that resolves this vulnerability.

    Fixed in 8.0.29
  31. Upgrade

    Upgrade nuget/Microsoft.NetCore.App.Runtime.linux-x64 to a version that resolves this vulnerability.

    Fixed in 8.0.29
  32. Upgrade

    Upgrade nuget/Microsoft.NetCore.App.Runtime.linux-musl-x64 to a version that resolves this vulnerability.

    Fixed in 8.0.29
  33. Upgrade

    Upgrade nuget/Microsoft.NetCore.App.Runtime.linux-musl-arm64 to a version that resolves this vulnerability.

    Fixed in 8.0.29
  34. Upgrade

    Upgrade nuget/Microsoft.NetCore.App.Runtime.linux-musl-arm to a version that resolves this vulnerability.

    Fixed in 8.0.29
  35. Upgrade

    Upgrade nuget/Microsoft.NetCore.App.Runtime.linux-arm64 to a version that resolves this vulnerability.

    Fixed in 8.0.29
  36. Upgrade

    Upgrade nuget/Microsoft.NetCore.App.Runtime.linux-arm to a version that resolves this vulnerability.

    Fixed in 8.0.29
  37. Upgrade

    Upgrade nuget/Microsoft.NetCore.App.Runtime.win-x86 to a version that resolves this vulnerability.

    Fixed in 9.0.18
  38. Upgrade

    Upgrade nuget/Microsoft.NetCore.App.Runtime.win-x64 to a version that resolves this vulnerability.

    Fixed in 9.0.18
  39. Upgrade

    Upgrade nuget/Microsoft.NetCore.App.Runtime.win-arm64 to a version that resolves this vulnerability.

    Fixed in 9.0.18
  40. Upgrade

    Upgrade nuget/Microsoft.NetCore.App.Runtime.win-arm to a version that resolves this vulnerability.

    Fixed in 9.0.18
  41. Upgrade

    Upgrade nuget/Microsoft.NetCore.App.Runtime.osx-x64 to a version that resolves this vulnerability.

    Fixed in 9.0.18
  42. Upgrade

    Upgrade nuget/Microsoft.NetCore.App.Runtime.osx-arm64 to a version that resolves this vulnerability.

    Fixed in 9.0.18
  43. Upgrade

    Upgrade nuget/Microsoft.NetCore.App.Runtime.linux-x64 to a version that resolves this vulnerability.

    Fixed in 9.0.18
  44. Upgrade

    Upgrade nuget/Microsoft.NetCore.App.Runtime.linux-musl-x64 to a version that resolves this vulnerability.

    Fixed in 9.0.18
  45. Upgrade

    Upgrade nuget/Microsoft.NetCore.App.Runtime.linux-musl-arm64 to a version that resolves this vulnerability.

    Fixed in 9.0.18
  46. Upgrade

    Upgrade nuget/Microsoft.NetCore.App.Runtime.linux-musl-arm to a version that resolves this vulnerability.

    Fixed in 9.0.18
  47. Upgrade

    Upgrade nuget/Microsoft.NetCore.App.Runtime.linux-arm64 to a version that resolves this vulnerability.

    Fixed in 9.0.18
  48. Upgrade

    Upgrade nuget/Microsoft.NetCore.App.Runtime.linux-arm to a version that resolves this vulnerability.

    Fixed in 9.0.18
  49. Upgrade

    Upgrade nuget/Microsoft.NetCore.App.Runtime.win-x86 to a version that resolves this vulnerability.

    Fixed in 10.0.10
  50. Upgrade

    Upgrade nuget/Microsoft.NetCore.App.Runtime.win-x64 to a version that resolves this vulnerability.

    Fixed in 10.0.10
  51. Upgrade

    Upgrade nuget/Microsoft.NetCore.App.Runtime.win-arm64 to a version that resolves this vulnerability.

    Fixed in 10.0.10
  52. Upgrade

    Upgrade nuget/Microsoft.NetCore.App.Runtime.win-arm to a version that resolves this vulnerability.

    Fixed in 10.0.10
  53. Upgrade

    Upgrade nuget/Microsoft.NetCore.App.Runtime.osx-x64 to a version that resolves this vulnerability.

    Fixed in 10.0.10
  54. Upgrade

    Upgrade nuget/Microsoft.NetCore.App.Runtime.osx-arm64 to a version that resolves this vulnerability.

    Fixed in 10.0.10
  55. Upgrade

    Upgrade nuget/Microsoft.NetCore.App.Runtime.linux-x64 to a version that resolves this vulnerability.

    Fixed in 10.0.10
  56. Upgrade

    Upgrade nuget/Microsoft.NetCore.App.Runtime.linux-musl-x64 to a version that resolves this vulnerability.

    Fixed in 10.0.10
  57. Upgrade

    Upgrade nuget/Microsoft.NetCore.App.Runtime.linux-musl-arm64 to a version that resolves this vulnerability.

    Fixed in 10.0.10
  58. Upgrade

    Upgrade nuget/Microsoft.NetCore.App.Runtime.linux-musl-arm to a version that resolves this vulnerability.

    Fixed in 10.0.10
  59. Upgrade

    Upgrade nuget/Microsoft.NetCore.App.Runtime.linux-arm64 to a version that resolves this vulnerability.

    Fixed in 10.0.10
  60. Upgrade

    Upgrade nuget/Microsoft.NetCore.App.Runtime.linux-arm to a version that resolves this vulnerability.

    Fixed in 10.0.10
  61. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 4.8.9340.0Patch KB5101002
  62. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 10.0.10Patch KB5104034
  63. Upgrade

    Upgrade System.Net.Mail/.NET SMTP client (System.Net.Mail) to a version that resolves this vulnerability.

    Patch CVE-2026-50659
  64. Upgrade

    Upgrade Microsoft.NetCore.App.Runtime.linux-arm64 (NuGet) to a version that resolves this vulnerability.

    Fixed in 10.0.10
  65. Upgrade

    Upgrade Microsoft.NetCore.App.Runtime.linux-arm64 (NuGet) to a version that resolves this vulnerability.

    Fixed in 8.0.29
  66. Upgrade

    Upgrade Microsoft.NetCore.App.Runtime.linux-arm64 (NuGet) to a version that resolves this vulnerability.

    Fixed in 9.0.18
  67. Upgrade

    Upgrade Microsoft.NetCore.App.Runtime.linux-arm (NuGet) to a version that resolves this vulnerability.

    Fixed in 10.0.10
  68. Upgrade

    Upgrade Microsoft.NetCore.App.Runtime.linux-arm (NuGet) to a version that resolves this vulnerability.

    Fixed in 8.0.29
  69. Upgrade

    Upgrade Microsoft.NetCore.App.Runtime.linux-arm (NuGet) to a version that resolves this vulnerability.

    Fixed in 9.0.18
  70. Upgrade

    Upgrade Microsoft.NetCore.App.Runtime.linux-musl-arm64 (NuGet) to a version that resolves this vulnerability.

    Fixed in 10.0.10
  71. Upgrade

    Upgrade Microsoft.NetCore.App.Runtime.linux-musl-arm64 (NuGet) to a version that resolves this vulnerability.

    Fixed in 8.0.29
  72. Upgrade

    Upgrade Microsoft.NetCore.App.Runtime.linux-musl-arm64 (NuGet) to a version that resolves this vulnerability.

    Fixed in 9.0.18
  73. Upgrade

    Upgrade Microsoft.NetCore.App.Runtime.linux-musl-arm (NuGet) to a version that resolves this vulnerability.

    Fixed in 10.0.10
  74. Upgrade

    Upgrade Microsoft.NetCore.App.Runtime.linux-musl-arm (NuGet) to a version that resolves this vulnerability.

    Fixed in 8.0.29
  75. Upgrade

    Upgrade Microsoft.NetCore.App.Runtime.linux-musl-arm (NuGet) to a version that resolves this vulnerability.

    Fixed in 9.0.18
  76. Upgrade

    Upgrade Microsoft.NetCore.App.Runtime.linux-musl-x64 (NuGet) to a version that resolves this vulnerability.

    Fixed in 10.0.10
  77. Upgrade

    Upgrade Microsoft.NetCore.App.Runtime.linux-musl-x64 (NuGet) to a version that resolves this vulnerability.

    Fixed in 8.0.29
  78. Upgrade

    Upgrade Microsoft.NetCore.App.Runtime.linux-musl-x64 (NuGet) to a version that resolves this vulnerability.

    Fixed in 9.0.18
  79. Upgrade

    Upgrade Microsoft.NetCore.App.Runtime.linux-x64 (NuGet) to a version that resolves this vulnerability.

    Fixed in 10.0.10
  80. Upgrade

    Upgrade Microsoft.NetCore.App.Runtime.linux-x64 (NuGet) to a version that resolves this vulnerability.

    Fixed in 8.0.29
  81. Upgrade

    Upgrade Microsoft.NetCore.App.Runtime.linux-x64 (NuGet) to a version that resolves this vulnerability.

    Fixed in 9.0.18
  82. Upgrade

    Upgrade Microsoft.NetCore.App.Runtime.osx-arm64 (NuGet) to a version that resolves this vulnerability.

    Fixed in 10.0.10
  83. Upgrade

    Upgrade Microsoft.NetCore.App.Runtime.osx-arm64 (NuGet) to a version that resolves this vulnerability.

    Fixed in 8.0.29
  84. Upgrade

    Upgrade Microsoft.NetCore.App.Runtime.osx-arm64 (NuGet) to a version that resolves this vulnerability.

    Fixed in 9.0.18
  85. Upgrade

    Upgrade Microsoft.NetCore.App.Runtime.osx-x64 (NuGet) to a version that resolves this vulnerability.

    Fixed in 10.0.10
  86. Upgrade

    Upgrade Microsoft.NetCore.App.Runtime.osx-x64 (NuGet) to a version that resolves this vulnerability.

    Fixed in 8.0.29
  87. Upgrade

    Upgrade Microsoft.NetCore.App.Runtime.osx-x64 (NuGet) to a version that resolves this vulnerability.

    Fixed in 9.0.18
  88. Upgrade

    Upgrade Microsoft.NetCore.App.Runtime.win-arm64 (NuGet) to a version that resolves this vulnerability.

    Fixed in 10.0.10
  89. Upgrade

    Upgrade Microsoft.NetCore.App.Runtime.win-arm64 (NuGet) to a version that resolves this vulnerability.

    Fixed in 8.0.29
  90. Upgrade

    Upgrade Microsoft.NetCore.App.Runtime.win-arm64 (NuGet) to a version that resolves this vulnerability.

    Fixed in 9.0.18
  91. Upgrade

    Upgrade Microsoft.NetCore.App.Runtime.win-arm (NuGet) to a version that resolves this vulnerability.

    Fixed in 10.0.10
  92. Upgrade

    Upgrade Microsoft.NetCore.App.Runtime.win-arm (NuGet) to a version that resolves this vulnerability.

    Fixed in 8.0.29
  93. Upgrade

    Upgrade Microsoft.NetCore.App.Runtime.win-arm (NuGet) to a version that resolves this vulnerability.

    Fixed in 9.0.18
  94. Upgrade

    Upgrade Microsoft.NetCore.App.Runtime.win-x64 (NuGet) to a version that resolves this vulnerability.

    Fixed in 10.0.10
  95. Upgrade

    Upgrade Microsoft.NetCore.App.Runtime.win-x64 (NuGet) to a version that resolves this vulnerability.

    Fixed in 8.0.29
  96. Upgrade

    Upgrade Microsoft.NetCore.App.Runtime.win-x64 (NuGet) to a version that resolves this vulnerability.

    Fixed in 9.0.18
  97. Upgrade

    Upgrade Microsoft.NetCore.App.Runtime.win-x86 (NuGet) to a version that resolves this vulnerability.

    Fixed in 10.0.10
  98. Upgrade

    Upgrade Microsoft.NetCore.App.Runtime.win-x86 (NuGet) to a version that resolves this vulnerability.

    Fixed in 8.0.29
  99. Upgrade

    Upgrade Microsoft.NetCore.App.Runtime.win-x86 (NuGet) to a version that resolves this vulnerability.

    Fixed in 9.0.18
  100. Operational

    After installing the updated runtime/SDK, restart apps so the update takes effect.

Event History

Jul 14, 2026
CVE Published
via Microsoft·02:00 PM
Data Sourced
via Microsoft·02:00 PM
DescriptionSeverityWeaknessAffected Software
Updated
via Microsoft·02:00 PM
Affected Software
Updated
via Microsoft·02:00 PM
Description
CVE Published
via MITRE·07:40 PM
Data Sourced
via MITRE·07:40 PM
DescriptionSeverity
Data Sourced
via NVD·08:17 PM
DescriptionSeverityWeakness
Data Sourced
via NVD·08:17 PM
RemedyAffected Software
Jul 16, 2026
Data Sourced
via Debian·03:46 AM
DescriptionAffected Software
Data Sourced
via Launchpad·03:46 AM
Description
Jul 18, 2026
Data Sourced
via Ubuntu·03:46 AM
RemedyDescriptionSeverityAffected Software
Jul 20, 2026
Advisory Published
via GitHub·11:02 PM
Data Sourced
via GitHub·11:02 PM
DescriptionSeverityWeaknessAffected Software

Frequently Asked Questions

1

What is the severity of CVE-2026-50659?

CVE-2026-50659 has a medium severity score of 6.5.

2

How do I fix CVE-2026-50659?

To fix CVE-2026-50659, update to the latest version of the Microsoft .NET Framework that addresses this vulnerability.

3

What is CVE-2026-50659 related to?

CVE-2026-50659 is related to a spoofing vulnerability in the .NET SMTP client (System.Net.Mail).

4

Who is affected by CVE-2026-50659?

Developers using vulnerable versions of Microsoft .NET Framework and related runtimes are affected by CVE-2026-50659.

5

What type of vulnerability is CVE-2026-50659?

CVE-2026-50659 is classified as a spoofing vulnerability.

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