CVE-2026-21218

.NET Spoofing Vulnerability

Published Feb 10, 2026 CVSS 3.1 · 7.5 High EPSS < 1% KEV · Not listed
Description
Improper handling of missing special element in .NET allows an unauthorized attacker to perform spoofing over a network.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-qvhc-9v3j-5rfw Microsoft Security Advisory CVE-2026-21218 | .NET Security Feature Bypass Vulnerability
Ubuntu USN Ubuntu USN USN-8025-1 .NET vulnerability
Ubuntu USN Ubuntu USN USN-8025-2 .NET vulnerability
History
Type Values Removed Values Added
First Time appeared Apple
Apple macos
Linux
Linux linux Kernel
Microsoft windows
CPEs cpe:2.3:o:apple:macos:-:*:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:-:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows:-:*:*:*:*:*:*:*
Vendors & Products Apple
Apple macos
Linux
Linux linux Kernel
Microsoft windows
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
Description Improper handling of missing special element in .NET allows an unauthorized attacker to perform spoofing over a network.
Title .NET Spoofing Vulnerability
First Time appeared Microsoft
Microsoft .net
Weaknesses CWE-166
CPEs cpe:2.3:a:microsoft:.net:*:*:*:*:*:*:*:*
Vendors & Products Microsoft
Microsoft .net
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N/E:U/RL:O/RC:C'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
microsoft
Published
Updated
Aug 19, 2026, 4:25 PM
Reserved
Dec 11, 2025, 9:02 PM
Status
Analyzed
Published
Feb 10, 2026, 6:16 PM
Modified
Jun 17, 2026, 10:18 AM