CVE-2026-32178: Microsoft Security Advisory CVE-2026-32178 – .NET Spoofing Vulnerability

April 14, 2026

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.

References

github.com/advisories/GHSA-vmwf-m9c5-3jvc
github.com/dotnet/announcements/issues/12345
github.com/dotnet/runtime
github.com/dotnet/runtime/security/advisories/GHSA-vmwf-m9c5-3jvc
msrc.microsoft.com/update-guide/vulnerability/CVE-2026-32178
nvd.nist.gov/vuln/detail/CVE-2026-32178

Code Behaviors & Features

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