Vulnerability · Published Feb 10, 2026 · Assigned by microsoft
CVE-2026-21218.NET Spoofing Vulnerability
High 7.5
In plain English
A high-severity security flaw in .NET 10.0 from Microsoft. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 1.0% (higher than 63% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Severity (CVSS 3.1)7.5High
Exploit odds (30 days)1.0%top 37.1% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
Official description
Improper handling of missing special element in .NET allows an unauthorized attacker to perform spoofing over a network.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine:v3.23 | dotnet10-runtime | 10.0.3-r0 | ALPINE-CVE-2026-21218 |
| Alpine:v3.24 | dotnet10-runtime | 10.0.3-r0 | ALPINE-CVE-2026-21218 |
| Alpine:v3.20 | dotnet8-runtime | 8.0.24-r0 | ALPINE-CVE-2026-21218 |
| Alpine:v3.21 | dotnet8-runtime | 8.0.24-r0 | ALPINE-CVE-2026-21218 |
| Alpine:v3.22 | dotnet8-runtime | 8.0.24-r0 | ALPINE-CVE-2026-21218 |
| Alpine:v3.23 | dotnet8-runtime | 8.0.24-r0 | ALPINE-CVE-2026-21218 |
| Alpine:v3.24 | dotnet8-runtime | 8.0.24-r0 | ALPINE-CVE-2026-21218 |
| Alpine:v3.21 | dotnet9-runtime | 9.0.13-r0 | ALPINE-CVE-2026-21218 |
| Alpine:v3.22 | dotnet9-runtime | 9.0.13-r0 | ALPINE-CVE-2026-21218 |
| Alpine:v3.23 | dotnet9-runtime | 9.0.13-r0 | ALPINE-CVE-2026-21218 |
| Alpine:v3.24 | dotnet9-runtime | 9.0.13-r0 | ALPINE-CVE-2026-21218 |
| NuGet | system.security.cryptography.cose | 10.0.3 | GHSA-qvhc-9v3j-5rfw |
| NuGet | system.security.cryptography.cose | 8.0.2 | GHSA-qvhc-9v3j-5rfw |
| NuGet | system.security.cryptography.cose | 9.0.13 | GHSA-qvhc-9v3j-5rfw |
| Ubuntu:24.04:LTS | dotnet10 | 10.0.103-10.0.3-0ubuntu1~24.04.1 | UBUNTU-CVE-2026-21218 |
| Ubuntu:24.04:LTS | dotnet10 | 10.0.103-10.0.3-0ubuntu1~24.04.1 | USN-8025-2 |
| Ubuntu:25.10 | dotnet10 | 10.0.103-10.0.3-0ubuntu1~25.10.1 | UBUNTU-CVE-2026-21218 |
| Ubuntu:25.10 | dotnet10 | 10.0.103-10.0.3-0ubuntu1~25.10.1 | USN-8025-1 |
| Ubuntu:22.04:LTS | dotnet6 | no fix listed | UBUNTU-CVE-2026-21218 |
| Ubuntu:22.04:LTS | dotnet7 | no fix listed | UBUNTU-CVE-2026-21218 |
| Ubuntu:22.04:LTS | dotnet8 | 8.0.124-8.0.24-0ubuntu1~22.04.1 | USN-8025-1 |
| Ubuntu:22.04:LTS | dotnet8 | 8.0.124-8.0.24-0ubuntu1~22.04.1 | UBUNTU-CVE-2026-21218 |
| Ubuntu:24.04:LTS | dotnet8 | 8.0.124-8.0.24-0ubuntu1~24.04.1 | UBUNTU-CVE-2026-21218 |
| Ubuntu:24.04:LTS | dotnet8 | 8.0.124-8.0.24-0ubuntu1~24.04.1 | USN-8025-2 |
| Ubuntu:25.10 | dotnet8 | 8.0.124-8.0.24-0ubuntu1~25.10.1 | USN-8025-1 |
| Ubuntu:25.10 | dotnet8 | 8.0.124-8.0.24-0ubuntu1~25.10.1 | UBUNTU-CVE-2026-21218 |
| Ubuntu:25.10 | dotnet9 | 9.0.114-9.0.13-0ubuntu1~25.10.1 | UBUNTU-CVE-2026-21218 |
| Ubuntu:25.10 | dotnet9 | 9.0.114-9.0.13-0ubuntu1~25.10.1 | USN-8025-1 |
Affected products (as reported)
Weakness: CWE-166 · 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
References
- .NET Spoofing Vulnerability vendor-advisory, patch