.NET
CVE-2026-21218 — .NET Spoofing Vulnerability
Executive Summary
Improper handling of missing special element in .NET allows an unauthorized attacker to perform spoofing over a network.
Overview
7.5
CVSS HIGH
Important
MS Severity
Not Exploited
MS Exploit Status
Exploitation Unlikely
MS Exploit Likelihood
CVSS 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
ATTACK VECTOR
Network
ATTACK COMPLEXITY
Low
PRIVILEGES REQUIRED
None
USER INTERACTION
None
SCOPE
Unchanged
CONFIDENTIALITY
None
INTEGRITY
High
AVAILABILITY
None
EXPLOIT CODE MATURITY
Unproven
REMEDIATION LEVEL
Official Fix
REPORT CONFIDENCE
Confirmed
Temporal Score: 6.5
EPSS Score
0.01015
probability of exploitation in the next 30 days
0.60257 percentile - updated 2026-08-14
View on FIRST.org
Affected Products
9 affected products
| Product | KB Article | Severity | Impact | Restart Required |
|---|---|---|---|---|
| .NET 10.0 installed on Linux | 5077862 (Security Update) |
Important | Spoofing | Maybe |
| .NET 10.0 installed on Mac OS | 5077862 (Security Update) |
Important | Spoofing | Maybe |
| .NET 10.0 installed on Windows | 5077862 (Security Update) |
Important | Spoofing | Maybe |
| .NET 8.0 installed on Linux | 5077863 (Security Update) |
Important | Spoofing | Maybe |
| .NET 8.0 installed on Mac OS | 5077863 (Security Update) |
Important | Spoofing | Maybe |
| .NET 8.0 installed on Windows | 5077863 (Security Update) |
Important | Spoofing | Maybe |
| .NET 9.0 installed on Linux | 5077864 (Security Update) |
Important | Spoofing | Maybe |
| .NET 9.0 installed on Mac OS | 5077864 (Security Update) |
Important | Spoofing | Maybe |
| .NET 9.0 installed on Windows | 5077864 (Security Update) |
Important | Spoofing | Maybe |
Patches
3 patches
| Article | Type | Restart |
|---|---|---|
5077862 |
Security Update | Maybe |
5077863 |
Security Update | Maybe |
5077864 |
Security Update | Maybe |
Exploits & PoC
No public exploit or PoC has been linked for this CVE yet. When available, references are sourced from public repositories and may be unverified or non-functional — review carefully before use.
Detection Rules
No public Sigma or Nuclei detection rule has been mapped to this CVE yet. Coverage is concentrated on exploited / high-profile vulnerabilities; check SigmaHQ for updates.
Acknowledgments
References
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