Microsoft Net Framework 4.0 V 30319 Vulnerabilities

Severity: 7.4 (High)
Vector: Remote Code Execution

ClickOnce deployment in .NET 4.0.30319 did not enforce HTTPS for manifest downloads correctly. An attacker on the same local network (or via ARP spoofing) could replace a legitimate .application manifest with a malicious one. The .NET Framework would trust the manifest if the signature was still valid—even if the content changed.

Real-world: This allowed attackers to push trojaned updates to enterprise internal tools.

Severity: Important (CVSS 6.8)
Affected Components: System.Web.Configuration.MachineKey microsoft net framework 4.0 v 30319 vulnerabilities

This is a cryptographic weakness in the way .NET 4.0 implemented the view state validation and forms authentication. An attacker could decrypt, tamper with, and re-encrypt authentication cookies.

Microsoft .NET Framework 4.0, with its specific build version 4.0.30319, was a landmark release in Microsoft’s software development platform. Released alongside Visual Studio 2010 and Windows Server 2008 R2, it introduced significant improvements in parallel computing, managed extensibility, and the Core Common Language Runtime (CLR).

However, version 4.0.30319 is now considered legacy and out-of-support (mainstream support ended in 2016, extended support ended in 2021). As a result, unpatched installations of this exact version contain numerous critical vulnerabilities that expose systems to remote code execution, privilege escalation, and denial-of-service attacks. Severity: 7

Important Note: The version string 4.0.30319 refers to the CLR build number. This same base version appears across Windows 7, Windows Server 2008 R2, and later OSes—but the vulnerability status depends entirely on the patch level (update rollup) applied to that build.

Microsoft .NET Framework 4.0 (v4.0.30319) is an unacceptable security risk in any production environment exposed to untrusted data or users. Its retirement means known, weaponized vulnerabilities (RCE, EoP, crypto attacks) remain unpatched. Organizations must prioritize migrating any application still locked to this runtime to .NET Framework 4.8 (which is fully backward compatible for 99% of 4.0 code) or .NET 6/8 (Core).

Treat any system reporting 4.0.30319 as a critical finding requiring immediate remediation. Important Note: The version string 4

The Risks of Staying on .NET Framework 4.0 (v4.0.30319) If you are seeing "4.0.30319" in your application headers or server logs, you might be sitting on a security time bomb. While this version was a milestone for Microsoft, it reached its end of support on January 12, 2016. This means Microsoft no longer provides technical support, automatic updates, or—most importantly—security fixes for this specific version. Why "v4.0.30319" Can Be Misleading

The version number 4.0.30319 refers to the Common Language Runtime (CLR). Because all versions of .NET Framework 4.x (from 4.0 up to 4.8.1) use this same CLR version, security scanners often flag it as vulnerable even if you have a newer, patched version of the framework installed.

However, if your application is truly targeting the original .NET 4.0, it is exposed to several critical vulnerabilities. Critical Vulnerabilities in .NET 4.0

Older versions of .NET 4.0 are susceptible to high-impact exploits that can lead to full system compromise: CLR 4.0.30319 vulnerabilities - asp.net - Stack Overflow

Here’s a solid, technically grounded summary of the known vulnerabilities for Microsoft .NET Framework 4.0 (version 4.0.30319) — noting that this specific version is end-of-life (EOL) and no longer receives security updates from Microsoft unless upgraded to a supported servicing baseline.