ADV200001 | Microsoft Guidance on Scripting Engine Memory Corruption Vulnerability

Security Advisory

Published: 01/17/2020 | Last Updated : 01/17/2020

A remote code execution vulnerability exists in the way that the scripting engine handles objects in memory in Internet Explorer. The vulnerability could corrupt memory in such a way that an attacker could execute arbitrary code in the context of the current user. 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.

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, for example, by sending an email.

Security Updates

To determine the support life cycle for your software version or edition, see the Microsoft Support Lifecycle.

Product	Platform	Article	Download	Impact	Severity	Supersedence
Internet Explorer 10	Windows Server 2012			Remote Code Execution	Moderate
Internet Explorer 11	Windows 10 Version 1803 for 32-bit Systems			Remote Code Execution	Critical
Internet Explorer 11	Windows 10 Version 1803 for x64-based Systems			Remote Code Execution	Critical
Internet Explorer 11	Windows 10 Version 1803 for ARM64-based Systems			Remote Code Execution	Critical
Internet Explorer 11	Windows 10 Version 1809 for 32-bit Systems			Remote Code Execution	Critical
Internet Explorer 11	Windows 10 Version 1809 for x64-based Systems			Remote Code Execution	Critical
Internet Explorer 11	Windows 10 Version 1809 for ARM64-based Systems			Remote Code Execution	Critical
Internet Explorer 11	Windows Server 2019			Remote Code Execution	Moderate
Internet Explorer 11	Windows 10 Version 1909 for 32-bit Systems			Remote Code Execution	Critical
Internet Explorer 11	Windows 10 Version 1909 for x64-based Systems			Remote Code Execution	Critical
Internet Explorer 11	Windows 10 Version 1909 for ARM64-based Systems			Remote Code Execution	Critical
Internet Explorer 11	Windows 10 Version 1709 for 32-bit Systems			Remote Code Execution	Critical
Internet Explorer 11	Windows 10 Version 1709 for x64-based Systems			Remote Code Execution	Critical
Internet Explorer 11	Windows 10 Version 1709 for ARM64-based Systems			Remote Code Execution	Critical
Internet Explorer 11	Windows 10 Version 1903 for 32-bit Systems			Remote Code Execution	Critical
Internet Explorer 11	Windows 10 Version 1903 for x64-based Systems			Remote Code Execution	Critical
Internet Explorer 11	Windows 10 Version 1903 for ARM64-based Systems			Remote Code Execution	Critical
Internet Explorer 11	Windows 10 for 32-bit Systems			Remote Code Execution	Critical
Internet Explorer 11	Windows 10 for x64-based Systems			Remote Code Execution	Critical
Internet Explorer 11	Windows 10 Version 1607 for 32-bit Systems			Remote Code Execution	Critical
Internet Explorer 11	Windows 10 Version 1607 for x64-based Systems			Remote Code Execution	Critical
Internet Explorer 11	Windows Server 2016			Remote Code Execution	Moderate
Internet Explorer 11	Windows 7 for 32-bit Systems Service Pack 1			Remote Code Execution	Critical
Internet Explorer 11	Windows 7 for x64-based Systems Service Pack 1			Remote Code Execution	Critical
Internet Explorer 11	Windows 8.1 for 32-bit systems			Remote Code Execution	Critical
Internet Explorer 11	Windows 8.1 for x64-based systems			Remote Code Execution	Critical
Internet Explorer 11	Windows RT 8.1			Remote Code Execution	Critical
Internet Explorer 11	Windows Server 2008 R2 for x64-based Systems Service Pack 1			Remote Code Execution	Moderate
Internet Explorer 11	Windows Server 2012			Remote Code Execution	Moderate
Internet Explorer 11	Windows Server 2012 R2			Remote Code Execution	Moderate
Internet Explorer 9	Windows Server 2008 for 32-bit Systems Service Pack 2			Remote Code Execution	Moderate
Internet Explorer 9	Windows Server 2008 for x64-based Systems Service Pack 2			Remote Code Execution	Moderate

Mitigations

By default, Internet Explorer on Windows Server 2008, Windows Server 2008 R2, Windows Server 2012, Windows Server 2012 R2, Windows Server 2016 and Windows Server 2019 runs in a restricted mode that is known as Enhanced Security Configuration. Enhanced Security Configuration is a group of preconfigured settings in Internet Explorer that can reduce the likelihood of a user or administrator downloading and running specially crafted web content on a server. This is a mitigating factor for websites that you have not added to the Internet Explorer Trusted sites zone.

Workarounds

Restrict access to JScript.dll

For 32-bit systems, enter the following command at an administrative command prompt:

cc]takeown /f %windir%\system32\jscript.dll
cacls %windir%\system32\jscript.dll /E /P everyone:N[/c]

For 64-bit systems, enter the following command at an administrative command prompt:

takeown /f %windir%\syswow64\jscript.dll
cacls %windir%\syswow64\jscript.dll /E /P everyone:N
takeown /f %windir%\system32\jscript.dll
cacls %windir%\system32\jscript.dll /E /P everyone:N

Impact of Workaround

Implementing these steps might result in reduced functionality for components or features that rely on jscript.dll. To be fully protected, Microsoft recommends the update be installed as soon as possible. Please revert the mitigation steps before installing the update to return to a full state.

By default, IE11, IE10, and IE9 uses Jscript9.dll which is not impacted by this vulnerability. This vulnerability only affects certain websites that utilize jscript as the scripting engine.

How to undo the workaround

For 32-bit systems, enter the following command at an administrative command prompt:

cacls %windir%\system32\jscript.dll /E /R everyone

For 64-bit systems, enter the following command at an administrative command prompt:

cacls %windir%\system32\jscript.dll /E /R everyone
cacls %windir%\syswow64\jscript.dll /E /R everyone

FAQ

Is there an update to address this vulnerability?
No, Microsoft is aware of this vulnerability and working on a fix. Our standard policy is to release security updates on Update Tuesday, the second Tuesday of each month. This predictable schedule allows for partner quality assurance and IT planning, which helps maintain the Windows ecosystem as a reliable, secure choice for our customers.

Is Microsoft aware of attacks based on this vulnerabilty?
Yes, Microsoft is aware of limited targeted attacks.

Is there a CVE assigned to this vulnerability?
Yes, Microsoft has assigned CVE-2020-0674 to this vulnerability

Acknowledgements

Clément Lecigne of Google’s Threat Analysis Group

Ella Yu from Qihoo 360

See acknowledgements for more information.

Disclaimer

The information provided in the Microsoft Knowledge Base is provided "as is" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.

Revisions

Version	Date	Description
1.0	01/17/2020	Information published.
1.1	01/17/2020	Added acknowledgements and an additional FAQ. This is an informational change only.

Source: https://portal.msrc.microsoft.com/en...sory/ADV200001

Posted By: Brink
18 Jan 2020