Microsoft Security Bulletin MS15-091 - Critical
Cumulative Security Update for Microsoft Edge (3084525)
Published: August 11, 2015
This security update resolves vulnerabilities in Microsoft Edge. The most severe of the vulnerabilities could allow remote code execution if a user views a specially crafted webpage using Microsoft Edge. An attacker who successfully exploited these vulnerabilities could gain the same user rights as the current user. Customers whose accounts are configured to have fewer user rights on the system could be less impacted than those who operate with administrative user rights.
This security update is rated Critical for Microsoft Edge on affected Windows clients. For more information, see the Affected Software section.
The security update addresses the vulnerabilities by:
- Modifying how Microsoft Edge handles objects in memory
- Helping to ensure that affected versions of Microsoft Edge properly implement the ASLR security feature
For more information about the vulnerabilities, see the Vulnerability Information section.
For more information about this update, see Microsoft Knowledge Base Article 3084525.
The following software versions or editions are affected. Versions or editions that are not listed are either past their support life cycle or are not affected. To determine the support life cycle for your software version or edition, see Microsoft Support Lifecycle.
|**Operating System**||**Component**||**Maximum Security Impact**||**Aggregate Severity Rating**||**Updates Replaced**|
|[Windows 10 for 32-bit Systems](https://support.microsoft.com/en-us/kb/3081436) (3081436)||Microsoft Edge||Remote Code Execution||Critical||None|
|[Windows 10 for x64-based Systems](https://support.microsoft.com/en-us/kb/3081436) (3081436)||Microsoft Edge||Remote Code Execution||Critical||None|
Severity Ratings and Vulnerability Identifiers
The following severity ratings assume the potential maximum impact of the vulnerability. For information regarding the likelihood, within 30 days of this security bulletin's release, of the exploitability of the vulnerability in relation to its severity rating and security impact, please see the Exploitability Index in the August bulletin summary.
Where specified in the Severity Ratings and Impact table, Critical, Important, and Moderate values indicate severity ratings. For more information, see Security Bulletin Severity Rating System. Refer to the following key for the abbreviations used in the table to indicate maximum impact:
|RCE||Remote Code Execution|
|EoP||Elevation of Privilege|
|SFB||Security Feature Bypass|
|**Vulnerability Severity Ratings and Impact**|
|**CVE number**||**Vulnerability Title**||**Microsoft Edge**|
|[CVE-2015-2441](http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=cve-2015-2441)||Memory Corruption Vulnerability||Windows Clients: **Critical / RCE** Windows Servers: **Moderate / RCE**|
|[CVE-2015-2442](http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=cve-2015-2442)||Memory Corruption Vulnerability||Windows Clients: **Critical / RCE** Windows Servers: **Moderate / RCE**|
|[CVE-2015-2446](http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=cve-2015-2446)||Memory Corruption Vulnerability||Windows Clients: **Critical / RCE** Windows Servers: **Moderate / RCE**|
|[CVE-2015-2449](http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=cve-2015-2449)||ASLR Bypass||Windows Clients: **Important / SFB** Windows Servers: **Low / SFB**|
Multiple Memory Corruption Vulnerabilities
Remote code execution vulnerabilities exist when Microsoft Edge 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 Microsoft Edge, 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 complete 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 Microsoft Edge 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 Microsoft Edge handles 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|
|Memory Corruption Vulnerability||CVE-2015-2441||No||No|
|Memory Corruption Vulnerability||CVE-2015-2442||No||No|
|Memory Corruption Vulnerability||CVE-2015-2446||No||No|
|Vulnerability title||CVE number||Publicly Disclosed||Exploited|