COURTESY NOTICE: CVE-2019-1367 Scripting Engine Memory Corruption Vulnerability

Microsoft released a critical patch yesterday which must be applied to all computers and servers because there is an exploit out in the wild (automated processes that seek un-patched systems) that can take over the computer or server and perform malicious tasks.

Please make sure you or your IT provider takes the steps needed to protect your business from this vulnerability or call me at 905-231-1303 if you have any questions or need assistance.

CVE-2019-1367 | Scripting Engine Memory Corruption Vulnerability

Security Vulnerability

Published: 09/23/2019
MITRE CVE-2019-1367

On this page

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.

The security update addresses the vulnerability by modifying how the scripting engine handles objects in memory.

Exploitability Assessment

The following table provides an exploitability assessment for this vulnerability at the time of original publication.
Publicly Disclosed	Exploited	Latest Software Release	Older Software Release	Denial of Service
No	Yes	0 – Exploitation Detected	0 – Exploitation Detected	Not Applicable

Security Updates
CVSS Score

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	4522007	IE Cumulative	Remote Code Execution	Moderate	4516046
Internet Explorer 11	Windows 10 Version 1703 for 32-bit Systems	4522011	Security Update	Remote Code Execution	Critical	4512574
Internet Explorer 11	Windows 10 Version 1703 for x64-based Systems	4522011	Security Update	Remote Code Execution	Critical	4512574
Internet Explorer 11	Windows 10 Version 1803 for 32-bit Systems	4522014	Security Update	Remote Code Execution	Critical	4512576
Internet Explorer 11	Windows 10 Version 1803 for x64-based Systems	4522014	Security Update	Remote Code Execution	Critical	4512576
Internet Explorer 11	Windows 10 Version 1803 for ARM64-based Systems	4522014	Security Update	Remote Code Execution	Critical	4512576
Internet Explorer 11	Windows 10 Version 1809 for 32-bit Systems	4522015	Security Update	Remote Code Execution	Critical	4512577
Internet Explorer 11	Windows 10 Version 1809 for x64-based Systems	4522015	Security Update	Remote Code Execution	Critical	4512577
Internet Explorer 11	Windows 10 Version 1809 for ARM64-based Systems	4522015	Security Update	Remote Code Execution	Critical	4512577
Internet Explorer 11	Windows Server 2019	4522015	Security Update	Remote Code Execution	Moderate	4512577
Internet Explorer 11	Windows 10 Version 1709 for 32-bit Systems	4522012	Security Update	Remote Code Execution	Critical	4512575
Internet Explorer 11	Windows 10 Version 1709 for 64-based Systems	4522012	Security Update	Remote Code Execution	Critical	4512575
Internet Explorer 11	Windows 10 Version 1709 for ARM64-based Systems	4522012	Security Update	Remote Code Execution	Critical	4512575
Internet Explorer 11	Windows 10 Version 1903 for 32-bit Systems	4522016	Security Update	Remote Code Execution	Critical	4512578
Internet Explorer 11	Windows 10 Version 1903 for x64-based Systems	4522016	Security Update	Remote Code Execution	Critical	4512578
Internet Explorer 11	Windows 10 Version 1903 for ARM64-based Systems	4522016	Security Update	Remote Code Execution	Critical	4512578
Internet Explorer 11	Windows 10 for 32-bit Systems	4522009	Security Update	Remote Code Execution	Critical	4511839
Internet Explorer 11	Windows 10 for x64-based Systems	4522009	Security Update	Remote Code Execution	Critical	4511839
Internet Explorer 11	Windows 10 Version 1607 for 32-bit Systems	4522010	Security Update	Remote Code Execution	Critical	4516044
Internet Explorer 11	Windows 10 Version 1607 for x64-based Systems	4522010	Security Update	Remote Code Execution	Critical	4516044
Internet Explorer 11	Windows Server 2016	4522010	Security Update	Remote Code Execution	Moderate	4516044
Internet Explorer 11	Windows 7 for 32-bit Systems Service Pack 1	4522007	IE Cumulative	Remote Code Execution	Critical	4516046
Internet Explorer 11	Windows 7 for x64-based Systems Service Pack 1	4522007	IE Cumulative	Remote Code Execution	Critical	4516046
Internet Explorer 11	Windows 8.1 for 32-bit systems	4522007	IE Cumulative	Remote Code Execution	Critical	4516046
Internet Explorer 11	Windows 8.1 for x64-based systems	4522007	IE Cumulative	Remote Code Execution	Critical	4516046
Internet Explorer 11	Windows Server 2008 R2 for x64-based Systems Service Pack 1	4522007	IE Cumulative	Remote Code Execution	Moderate	4516046
Internet Explorer 11	Windows Server 2012	4522007	IE Cumulative	Remote Code Execution	Moderate	4516046
Internet Explorer 11	Windows Server 2012 R2	4522007	IE Cumulative	Remote Code Execution	Moderate	4516046
Internet Explorer 9	Windows Server 2008 for 32-bit Systems Service Pack 2	4522007	IE Cumulative	Remote Code Execution	Moderate	4516046
Internet Explorer 9	Windows Server 2008 for x64-based Systems Service Pack 2	4522007	IE Cumulative	Remote Code Execution	Moderate	4516046

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:

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

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

Will an updated Windows Update offline scan file, Wsusscn2.cab, with this new security update be available?

No, an updated scan file will not be available until the next security release in October 2019. As a workaround, you will need to download the September 2019 WSUS scan cab and then manually download this update from Microsoft Update Catalog to deploy.

Acknowledgements

Clément Lecigne of Google’s Threat Analysis Group

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	09/23/2019	Information published.