09 December 2015
Protect yourself against future threats.
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2015.3064 Microsoft Security Bulletin MS15-129: Security Update for Silverlight to Address Remote Code Execution (3106614) 9 December 2015 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: Microsoft Silverlight Publisher: Microsoft Operating System: Windows Mac OS Impact/Access: Execute Arbitrary Code/Commands -- Remote with User Interaction Access Confidential Data -- Remote with User Interaction Resolution: Patch/Upgrade CVE Names: CVE-2015-6166 CVE-2015-6165 CVE-2015-6114 Original Bulletin: https://technet.microsoft.com/en-us/library/security/MS15-129 - --------------------------BEGIN INCLUDED TEXT-------------------- Microsoft Security Bulletin MS15-129: Security Update for Silverlight to Address Remote Code Execution (3106614) Document Metadata Bulletin Number: MS15-129 Bulletin Title: Security Update for Silverlight to Address Remote Code Execution Severity: Critical KB Article: 3106614 Version: 1.0 Published Date: December 8, 2015 Executive Summary This security update resolves vulnerabilities in Microsoft Silverlight. The most severe of the vulnerabilities could allow remote code execution if Microsoft Silverlight incorrectly handles certain open and close requests that could result in read- and write-access violations. To exploit the vulnerability, an attacker could host a website that contains a specially crafted Silverlight application and then convince a user to visit a compromised website. The attacker could also take advantage of websites containing specially crafted content, including those that accept or host user-provided content or advertisements. An attacker would have no way to force users to visit a compromised website. Instead, an attacker would have to convince a user to take action, such as clicking a link that takes the user to the attacker's website. This security update is rated Critical for Microsoft Silverlight 5 and Microsoft Silverlight 5 Developer Runtime when installed on Mac or all supported releases of Microsoft Windows. For more information, see the Affected Software section. Affected Software Microsoft Silverlight 5 Microsoft Silverlight 5 Developer Runtime Vulnerability Information Microsoft Silverlight RCE Vulnerability - CVE-2015-6166 A remote code execution vulnerability exists when Microsoft Silverlight incorrectly handles certain open and close requests that can result in read- and write-access violations. To exploit the vulnerability, an attacker could host a website that contains a specially crafted Silverlight application and then convince a user to visit the compromised website. The attacker could also take advantage of websites containing specially crafted content, including those that accept or host user-provided content or advertisements. For example, an attacker could display specially crafted web content by using banner advertisements or by using other methods to deliver web content to affected systems. In all cases, however, an attacker would have no way to force users to visit a compromised website. Instead, an attacker would have to convince a user to visit the website, typically by enticing the user to click a link in an email or in an Instant Messenger message. In the web-browsing scenario, an attacker who successfully exploited this vulnerability could obtain the same permissions as the currently logged-on user. If a user is logged on with administrative user rights, an attacker could take complete control of the affected system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights. The update addresses the vulnerability by correcting how Microsoft Silverlight handles certain open and close web requests. Microsoft received information about this vulnerability through coordinated vulnerability disclosure. At the time this security bulletin was originally issued, Microsoft was unaware of any attack attempting to exploit this vulnerability. Multiple Microsoft Silverlight Information Disclosure Vulnerabilities Multiple information disclosure vulnerabilities exist when Silverlight fails to properly handle objects in memory, which could allow an attacker to more reliably predict pointer values and degrade the efficacy of the Address Space Layout Randomization (ASLR) security feature. To exploit the vulnerabilities, in a web-browsing attack scenario, an attacker could potentially bypass the ASLR security feature, which protects users from a broad class of vulnerabilities. The ASLR bypass by itself does not allow arbitrary code execution. However, an attacker could use the vulnerabilities in conjunction with an ASLR bypass to compromise a targeted system. In a web-based attack scenario, an attacker could host a website with specially crafted Silverlight content in an attempt to exploit the vulnerabilities. In addition, compromised websites and websites that accept or host user-provided content containing specially crafted content could also exploit the vulnerabilities. An attacker would have no way to force a user to visit a specially crafted website. Instead, an attacker would have to convince a user to take action. For example, an attacker could trick a user into clicking a link that takes the user to the attacker's website. The update addresses the vulnerabilities by correcting how memory is handled to maintain the integrity of ASLR in Silverlight. Microsoft received information about the vulnerabilities through coordinated vulnerability disclosure. At the time this security bulletin was originally issued, Microsoft was unaware of any attack attempting to exploit the vulnerabilities. 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 Microsoft Silverlight Information Disclosure Vulnerability CVE-2015-6114 No No Microsoft Silverlight Information Disclosure Vulnerability CVE-2015-6165 No No - --------------------------END INCLUDED TEXT-------------------- You have received this e-mail bulletin as a result of your organisation's registration with AusCERT. The mailing list you are subscribed to is maintained within your organisation, so if you do not wish to continue receiving these bulletins you should contact your local IT manager. If you do not know who that is, please send an email to firstname.lastname@example.org and we will forward your request to the appropriate person. NOTE: Third Party Rights This security bulletin is provided as a service to AusCERT's members. 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