Multiple serious vulnerabilities have been found in Microsoft .NET Framework. Malicious users can exploit these vulnerabilities to cause denial of service, bypass security restrictions fain privileges, execute arbitrary code or obtain sensitive information.

Below is a complete list of vulnerabilities

1. An improper ASLR implementation can be exploited remotely via a specially designed web site or memory addresses prediction;
2. Unverified data processing can be exploited remotely via vectors related to Internet Explorer;
3. An improper hash table usage can be exploited remotely via a specially designed request;
4. Improper TypeFilterLevel checking can be exploited remotely via .NET Remoting manipulations;
5. Improper IRI parsing can be exploited remotely via a specially designed request;
6. Unsafe method execution can be exploited remotely via a specially designed .NET application;
7. Improper TCP connections handling can be exploited remotely via a specially designed HTTP requests;
8. An improper memory access restrictions can be exploited remotely via vectors related to malformed objects.

Microsoft .NET Framework version 1.0 Service Pack 3
Microsoft .NET Framework version 1.1 Service Pack 1
Microsoft .NET Framework version 2.0 Service Pack 2
Microsoft .NET Framework versions 3.5, 3.5.1, 4, 4.5, 4.5.1

Install necessary updates from the KB section, that are listed in your Windows Update (Windows Update usually can be accessed from the Control Panel)

CVE-2014-4072
CVE-2014-0257
CVE-2014-0253
CVE-2014-0295
CVE-2014-4149
CVE-2014-4122
CVE-2014-4121
CVE-2014-4062
CVE-2014-4073
CVE-2014-1806

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The following public exploits exists for this vulnerability:

https://www.exploit-db.com/exploits/33892

Malware exists for this vulnerability. Usually such malware is classified as Exploit. More details.