Perhaps the most alarming finding is CVE-2020-1046 (and its variants), which affects the way v4.0.30319 handles URL redirects in the HttpWebRequest object. By combining this with a lack of proper TLS certificate validation in older builds, an attacker performing a man-in-the-middle (MitM) attack could redirect a .NET application to a malicious update server or a UNC path ( \\evil\share\malicious.dll ) leading to RCE.
One notable historical vulnerability in this category involved the way .NET handled XML signatures. By exploiting flaws in the validation process, attackers could bypass security checks and gain unauthorized access to system resources. Denial of Service Weaknesses microsoft net framework 4.0 v 30319 vulnerabilities