Zero-day vulnerability in Microsoft .NET Framework

Improper input validation
CVE-2017-8759

The vulnerability was detected by FireEye  researchers. The attacker used Microsoft Office RTF document to leverage RCE in .NET Framework and deploy FINSPY malware. The malicious document тАЬ╨Я╤А╨╛╨╡╨║╤В.docтАЭ (MD5: fe5c4d6bb78e170abf5cf3741868ea4c) had Russian name and might have been used to target a Russian speaker.

Known malware:

FINSPY

Vulnerability details

Advisory: SB2017091210 - Remote code execution in Microsoft .NET Framework

Vulnerable component: Microsoft .NET Framework

CVE-ID: CVE-2017-8759

CVSSv3 score: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H/E:H/RL:O/RC:C

CWE-ID: CWE-20 - Improper input validation

Description:

The vulnerability allows a remote attacker to execute arbitrary code on the target system.

The vulnerability exists due to uncpecified error when processing untrusted input. A remote unauthenticated attacker can execute arbitrary code on the target system.

Successful exploitation of this vulnerability may result in complete compromise of vulnerable system.

Note: this vulnerability is being actively exploited in the wild.

Public Exploits:

- Microsoft Windows .NET Framework - Remote Code Execution [Exploit-DB]

External links:

https://www.fireeye.com/blog/threat-research/2017/09/zero-day-used-to-distribute-finspy.html

About zero-day vulnerabilities

Zero-day vulnerability is an undisclosed vulnerability in software that hackers can exploit to compromise computer programs, gain unauthorized access to sensitive data, penetrate networks, etc. We consider vulnerability a zero-day when there is no solution provided from software vendor and the vulnerability is being actively exploited by malicious actors.

Zero-day candidate is a potential zero-day vulnerability in software which might have been used in targeted attacks, however there is no evidence to support this suggestion.