Security Update for JScript and VBScript to Address Remote Code Execution (MS15-126)

ITS Advisory Number: 
2015-145
Date(s) Issued: 
Tuesday, December 8, 2015
Subject: 
Security Update for JScript and VBScript to Address Remote Code Execution (MS15-126)
Overview: 

This security update resolves vulnerabilities in the VBScript and JScript scripting engines in Microsoft Windows. The more severe of the vulnerabilities could allow remote code execution if an attacker hosts a specially crafted website that is designed to exploit the vulnerabilities through Internet Explorer (or leverages a compromised website or a website that accepts or hosts user-provided content or advertisements) and then convinces a user to view the website. An attacker could also embed an ActiveX control marked "safe for initialization" in an application or Microsoft Office document that uses the IE rendering engine to direct the user to the specially crafted website.

 

An attacker who successfully exploited the vulnerabilities could gain the same user rights as the current user and, if the current user is logged on with administrative user rights, the attacker could take control of an affected system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights.

Systems Affected: 
  • Microsoft Windows Vista Service Pack 2
  • Microsoft Windows Vista x64 Edition Service Pack 2
  • Windows Server 2008 for 32-bit Systems Service Pack 2
  • Windows Server 2008 for x64-based Systems Service Pack 2
  • Windows Server 2008 for Itanium-based Systems Service Pack 2
  • Windows Server 2008 for 32-bit Systems Service Pack 2 (Server Core installation)
  • Windows Server 2008 for x64-based Systems Service Pack 2 (Server Core installation)
  • Windows Server 2008 R2 for x64-based Systems Service Pack 1

    (Server Core installation only)
RISK
GOVERNMENT
Large and medium government entities: 
High
Small government entities: 
High
BUSINESS
Large and medium business entities: 
High
Small business entities: 
High
Home Users: 
High
Description: 

There are two vulnerabilities associated with this advisory;

  • Scripting Engine Information Disclosure Vulnerability (CVE-2015-6135) - An information disclosure vulnerability exists when VBScript improperly discloses the contents of its memory, which could provide an attacker with information to further compromise the user's computer or data.To exploit the vulnerability, an attacker must know the memory address of where the object was created. The update addresses the vulnerability by changing the way certain functions handle objects in memory.
  • Scripting Engine Memory Corruption Vulnerability (CVE-2015-6136) - A remote code execution vulnerability exists in the way that the VBScript engine renders, when handling objects in memory in Internet Explorer. In a web-based attack scenario, an attacker could host a specially crafted website that is designed to exploit the vulnerability through Internet Explorer and then convince a user to view the website. An attacker could also embed an ActiveX control marked "safe for initialization" in an application or Microsoft Office document that hosts the IE rendering engine. The attacker could also take advantage of compromised websites, and websites that accept or host user-provided content or advertisements. These websites could contain specially crafted content that could exploit the vulnerability.

An attacker who successfully exploited the vulnerability could gain the same user rights as the current user. If the current user is logged on with administrative user rights, an attacker who successfully exploited the vulnerability could take control of an affected system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights. The update addresses the vulnerability by modifying how the VBScript scripting engine handle objects in memory. 

Actions: 
  • After appropriate testing, apply appropriate patches provided by Microsoft to vulnerable systems.
  • Consider implementing the workarounds provided by Microsoft if patching cannot be completed immediately. (https://technet.microsoft.com/library/security/ms15-126).
  • Remind users not to visit un-trusted websites or follow links provided by unknown or un-trusted sources.
  • Run all software as a non-privileged user (one without administrative privileges) to diminish the effects of a successful attack.