Microsoft Net Framework 4.0 V 30319 Vulnerabilities May 2026

4.0.30319

The version number does not refer to a single vulnerable software version, but rather to the Common Language Runtime (CLR) 4.0 , which serves as the foundational engine for all .NET Framework versions from 4.0 through 4.8.1. While the runtime version string remains static, the underlying framework receives continuous security patches through Windows Update. Vulnerability Landscape

• How it works in v4.0.30319: The parser fails to properly validate input when handling a isOptional parameter in a WSDL definition. This leads to a remote code execution scenario when the .NET Framework processes the crafted SOAP response.
• Real-world exploitation: This vulnerability was weaponized by the FINDUCKET group and used in phishing campaigns targeting financial institutions.
• Mitigation in 4.0: Microsoft released a patch (KB4041085) in September 2017. However, because 4.0 is EOL, only customers with extended support contracts received it.

. Since that date, Microsoft has not provided security updates, technical support, or hotfixes for this specific version. Key Security Vulnerabilities microsoft net framework 4.0 v 30319 vulnerabilities

Check the Registry:

Navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\NET Framework Setup\NDP\v4\Full . Check the Release DWORD value. How it works in v4

Remote Code Execution (RCE):

Attackers can take complete control of a system by passing crafted input to susceptible .NET methods that fail to validate input correctly. . Since that date

Severity:

Important (CVSS 7.5) Affected Components: System.Security.Permissions.FileIOPermission

Treat any system reporting 4.0.30319 as a critical finding requiring immediate remediation.

Public-facing ASP.NET web app

| Attack Vector | Prerequisite | Exploit Availability | |---------------|--------------|----------------------| | | .NET 4.0, Forms Auth enabled | Metasploit module for CVE-2010-3332 | | WCF / .NET Remoting endpoint on internet | Unpatched TCP/HTTP channel | Public PoC for deserialization (CVE-2017-0248) | | Local privilege escalation | Malicious app running on same server | Use BinaryFormatter on untrusted data | | Email / file upload parsers | App uses XAML or XPS handling | CVE-2015-6092 (XAML Browser Applications) |