Multiple Memory Corruption Vulnerabilities in Internet Explorer
Remote code execution vulnerabilities exist when Internet Explorer improperly accesses objects in memory.

These vulnerabilities could corrupt memory in such a way that an attacker could execute arbitrary code in the context of the current user.
An attacker could host a specially crafted website that is designed to exploit these vulnerabilities through Internet Explorer, and then convince a user to view the website.

The attacker could also take advantage of compromised websites and websites that accept or host user-provided content or advertisements by adding specially crafted content that could exploit these vulnerabilities.
In all cases, however, an attacker would have no way to force users to view the attacker-controlled content.
Instead, an attacker would have to convince users to take action, typically by getting them to click a link in an instant messenger or email message that takes users to the attacker’s website, or by getting them to open an attachment sent through email.
An attacker who successfully exploited these vulnerabilities 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 these vulnerabilities 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 where Internet Explorer is used frequently, such as workstations or terminal servers, are at the most risk from these vulnerabilities.
The update addresses the vulnerabilities by modifying how Internet Explorer handles objects in memory.

The following table contains links to the standard entry for each vulnerability in the Common Vulnerabilities and Exposures list:

Mitigating Factors
Microsoft has not identified any mitigating factors for these vulnerabilities.

Workarounds
Microsoft has not identified any workarounds for these vulnerabilities.

FAQ
I am running Internet Explorer on Windows Server 2008, Windows Server 2008 R2, Windows Server 2012, or Windows Server 2012 R2.

Does this mitigate these vulnerabilities? Yes.

By default, Internet Explorer on Windows Server 2008, Windows Server 2008 R2, Windows Server 2012, and Windows Server 2012 R2 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.
Can EMET help mitigate attacks that attempt to exploit these vulnerabilities? Yes.

The Enhanced Mitigation Experience Toolkit (EMET) enables users to manage security mitigation technologies that help make it more difficult for attackers to exploit memory corruption vulnerabilities in a given piece of software.

EMET can help mitigate attacks that attempt to exploit these vulnerabilities in Internet Explorer on systems where EMET is installed and configured to work with Internet Explorer.
For more information about EMET, see the Enhanced Mitigation Experience Toolkit.

Scripting Engine Memory Corruption Vulnerability – CVE-2015-2493
A remote code execution vulnerability exists in the way that the VBScript and JScript engines, when rendered in Internet Explorer, handle objects in memory.
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 and JScript scripting engines handle objects in memory.
Microsoft received information about this vulnerability through coordinated vulnerability disclosure. When this security bulletin was originally issued, Microsoft had not received any information to indicate that the vulnerability had been publicly used to attack customers.

Vulnerability title

CVE number

Publicly disclosed

Exploited

Scripting Engine Memory Corruption Vulnerability

CVE-2015-2493

No

No

Mitigating Factors
Microsoft has not identified any mitigating factors for this vulnerability.

Workarounds
The following workarounds may be helpful in your situation:
Restrict access to VBScript.dll and JScript.dll
For 32-bit systems, enter the following command at an administrative command prompt:

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

Impact of Workaround. Websites that use VBScript or JScript may not work properly.
How to undo the workaround.
For 32-bit systems, enter the following command at an administrative command prompt:

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

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

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

Elevation of Privilege Vulnerability – CVE-2015-2489
An elevation of privilege vulnerability exists when Internet Explorer does not properly validate permissions under specific conditions, potentially allowing a script to be run with elevated privileges.
In a web-based attack scenario, an attacker could host a website that is used to attempt to exploit this vulnerability.
In addition, compromised websites and websites that accept or host user-provided content could contain specially crafted content that could exploit this vulnerability.
In all cases, however, an attacker would have no way to force users to view the attacker-controlled content.
Instead, an attacker would have to convince users to take action.

For example, an attacker could trick users into clicking a link that takes them to the attacker’s site.

An attacker who successfully exploited the vulnerability could elevate privileges in affected versions of Internet Explorer.
The vulnerability by itself does not allow arbitrary code to be run. However, the vulnerability could be used in conjunction with another vulnerability (e.g., a remote code execution vulnerability) that could take advantage of the elevated privileges when running arbitrary code.

For example, an attacker could exploit another vulnerability to run arbitrary code through Internet Explorer, but due to the context in which processes are launched by Internet Explorer, the code might be restricted to run at a low integrity level (very limited permissions). However, an attacker could, in turn, exploit the vulnerability to cause the arbitrary code to run at a medium integrity level (permissions of the current user).
The update addresses the vulnerability by adding additional permission validations to Internet Explorer.

The following table contains links to the standard entry for the vulnerability in the Common Vulnerabilities and Exposures list:

Vulnerability title

CVE number

Publicly disclosed

Exploited

Elevation of Privilege Vulnerability

CVE-2015-2489

No

No

Mitigating Factors
Microsoft has not identified any mitigating factors for this vulnerability.

Workarounds
Microsoft has not identified any workarounds for this vulnerability.

Information Disclosure Vulnerability – CVE-2015-2483
An information disclosure vulnerability exists when Internet Explorer improperly discloses the contents of its memory, which could provide an attacker with information to further compromise the user’s computer.

The update addresses the vulnerability by changing the way certain functions handle objects in memory.
The following table contains links to the standard entry for each vulnerability in the Common Vulnerabilities and Exposures list:

Vulnerability title

CVE number

Publicly disclosed

Exploited

Information Disclosure Vulnerability

CVE-2015-2483

No

No

Mitigating Factors
Microsoft has not identified any mitigating factors for this vulnerability.

Workarounds
Microsoft has not identified any workarounds for this vulnerability.

Information Disclosure Vulnerability – CVE-2015-2496
An information disclosure vulnerability exists in the way that certain functions handle objects in memory.

The vulnerability could allow an attacker to detect specific files on the user’s computer.
In a web-based attack scenario an attacker could host a website that is used to attempt to exploit the vulnerabilities.

Additionally, compromised websites and websites that accept or host user-provided content could contain specially crafted content that could be used to exploit the vulnerabilities. However, in all cases an attacker would have no way to force users to view attacker-controlled content.
Instead, an attacker would have to convince users to take action.

For example, an attacker could trick users into clicking a link that takes them to the attacker’s site.
The security update addresses the vulnerability by correcting how certain functions handle objects in memory.
The following table contains links to the standard entry for each vulnerability in the Common Vulnerabilities and Exposures list:

Vulnerability title

CVE number

Publicly disclosed

Exploited

Information Disclosure Vulnerability

CVE-2015-2496

Yes

Yes

Mitigating Factors
Microsoft has not identified any mitigating factors for this vulnerability.

Workarounds
Microsoft has not identified any workarounds for this vulnerability.

Tampering Vulnerability – CVE-2015-2484
A tampering vulnerability exists when Internet Explorer accesses a file with an improper flag that in turn permits a file operation.

This could allow a low privilege process to delete arbitrary files on the local system.

This update addresses the vulnerability by properly masking this flag off.
The following table contains links to the standard entry for each vulnerability in the Common Vulnerabilities and Exposures list:

Vulnerability title

CVE number

Publicly disclosed

Exploited

Tampering Vulnerability

CVE-2015-2484

No

No

Mitigating Factors
Microsoft has not identified any mitigating factors for this vulnerability.

Workarounds
Microsoft has not identified any workarounds for this vulnerability.

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