CVE-2018-8356 — System.Private.ServiceMod…
MEDIUMCVE-2018-8356 is a medium-severity (CVSS 5.5) CWE-295 vulnerability in System.Private.ServiceModel. A fix is available for System.Private.ServiceModel — see the affected versions and patch details below.
Improper Certificate Validation in Microsoft .NET Framework components
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
System.Private.ServiceModel.NETSystem.Private.ServiceModel.NETSystem.Private.ServiceModel.NETSystem.Private.ServiceModel.NETSystem.ServiceModel.Duplex.NETSystem.ServiceModel.Duplex.NETSystem.ServiceModel.Duplex.NETSystem.ServiceModel.Duplex+16 moreReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects NuGet packages — download data is not available via public APIs for these ecosystems.
Description
A security feature bypass vulnerability exists when Microsoft .NET Framework components do not correctly validate certificates, aka ".NET Framework Security Feature Bypass Vulnerability." This affects .NET Framework 4.7.2, Microsoft .NET Framework 3.0, Microsoft .NET Framework 4.6.2/4.7/4.7.1/4.7.2, ASP.NET Core 1.1, Microsoft .NET Framework 4.5.2, ASP.NET Core 2.0, ASP.NET Core 1.0, .NET Core 1.1, Microsoft .NET Framework 3.5, Microsoft .NET Framework 3.5.1, Microsoft .NET Framework 4.6/4.6.1/4.6.2, .NET Core 1.0, .NET Core 2.0, Microsoft .NET Framework 4.6, Microsoft .NET Framework 4.6/4.6.1/4.6.2/4.7/4.7.1/4.7.1/4.7.2, Microsoft .NET Framework 4.7.2.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| .NETNuGet | System.Private.ServiceModel | ≥ 4.0.0&&< 4.1.3 | 4.1.3dotnet add package System.Private.ServiceModel --version 4.1.3 |
| .NETNuGet | System.Private.ServiceModel | ≥ 4.3.0&&< 4.3.3 | 4.3.3dotnet add package System.Private.ServiceModel --version 4.3.3 |
| .NETNuGet | System.Private.ServiceModel | ≥ 4.4.0&&< 4.4.4 | 4.4.4dotnet add package System.Private.ServiceModel --version 4.4.4 |
| .NETNuGet | System.Private.ServiceModel | ≥ 4.5.0&&< 4.5.3 | 4.5.3dotnet add package System.Private.ServiceModel --version 4.5.3 |
| .NETNuGet | System.ServiceModel.Duplex | ≥ 4.3.0&&< 4.3.3 | 4.3.3dotnet add package System.ServiceModel.Duplex --version 4.3.3 |
| .NETNuGet | System.ServiceModel.Duplex | ≥ 4.4.0&&< 4.4.4 | 4.4.4dotnet add package System.ServiceModel.Duplex --version 4.4.4 |
Affected Products
.net coremicrosoft.net frameworkmicrosoft.net framework developer packmicrosoftasp.net coremicrosoftpowershell coremicrosoftDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for System.Private.ServiceModel, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update System.Private.ServiceModel to 4.1.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2018-8356 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
Frequently Asked Questions
Is CVE-2018-8356 in your dependencies?
Find it across NuGet, including transitive dependencies.