What is CVE-2026-21218?

CVE-2026-21218 is a security advisory published by Microsoft Security Response Center (MSRC) with High severity. .NET Spoofing Vulnerability

Which CVE IDs does CVE-2026-21218 cover?

CVE-2026-21218 covers the following CVE IDs: CVE-2026-21218. Each CVE has its own detail page on EchelonGraph Pulse with the synthesized EG score.

What is the CVSS v3 score of CVE-2026-21218?

CVE-2026-21218 has a CVSS v3 base score of 7.5, published by Microsoft Security Response Center (MSRC).

Which products are affected by CVE-2026-21218?

CVE-2026-21218 affects 9 products, including: .NET 10.0 installed on Linux; .NET 10.0 installed on Mac OS; .NET 10.0 installed on Windows; .NET 8.0 installed on Linux; .NET 8.0 installed on Mac OS; and others — see the full list on the advisory page.

CVE-2026-21218HighCVSS 7.5

.NET Spoofing Vulnerability

Vendor

Microsoft Security Response Center (MSRC)

Published

February 10, 2026

Last Modified

—

🔗 CVE IDs covered (1)

CVE-2026-21218 →

📋 Description

Improper handling of missing special element in .NET allows an unauthorized attacker to perform spoofing over a network.

🎯 Affected products9

.NET 10.0 installed on Linux
.NET 10.0 installed on Mac OS
.NET 10.0 installed on Windows
.NET 8.0 installed on Linux
.NET 8.0 installed on Mac OS
.NET 8.0 installed on Windows
.NET 9.0 installed on Linux
.NET 9.0 installed on Mac OS
.NET 9.0 installed on Windows

✅ Remediation

KB5077862 (Security Update) — fixed build 10.0.3 KB5077863 (Security Update) — fixed build 8.0.24 KB5077864 (Security Update) — fixed build 9.0.13

🔗 References (7)

advisoryhttps://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21218
patchhttps://dotnet.microsoft.com/download/dotnet/10.0
referencehttps://support.microsoft.com/help/5077862
patchhttps://dotnet.microsoft.com/download/dotnet/8.0
referencehttps://support.microsoft.com/help/5077863
patchhttps://dotnet.microsoft.com/download/dotnet/9.0
referencehttps://support.microsoft.com/help/5077864