CVE-2015-6164 in Silverlight
Summary
by MITRE
Microsoft Internet Explorer 9 through 11 improperly implements a cross-site scripting (XSS) protection mechanism, which allows remote attackers to bypass the Same Origin Policy via a crafted web site, aka "Internet Explorer XSS Filter Bypass Vulnerability."
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 11/18/2024
The vulnerability identified as CVE-2015-6164 represents a critical flaw in Microsoft Internet Explorer's security architecture that specifically affects versions 9 through 11. This issue resides within the browser's implementation of cross-site scripting protection mechanisms, creating a significant bypass opportunity for malicious actors. The vulnerability stems from the improper handling of the Same Origin Policy, which is a fundamental security principle that restricts how documents or scripts loaded from one origin can interact with resources from another origin. When this policy is compromised, it allows attackers to execute unauthorized operations across different domains, fundamentally undermining web security.
The technical implementation flaw manifests in how Internet Explorer's XSS filter processes and validates incoming web content. The filter, designed to prevent malicious scripts from executing in the context of a user's session, contains a logic error that permits crafted malicious payloads to circumvent the intended protection. This bypass occurs when attackers construct specially formatted web pages that exploit the filter's failure to properly validate or sanitize input parameters. The vulnerability specifically targets the browser's attempt to prevent XSS attacks by leveraging a weakness in the filter's detection algorithms, allowing attackers to inject malicious scripts that would normally be blocked.
The operational impact of this vulnerability extends beyond simple script execution, as it enables attackers to perform session hijacking, data theft, and unauthorized actions on behalf of users. When exploited, the vulnerability allows remote attackers to bypass the browser's security boundaries and access resources that should be restricted to the same origin. This creates opportunities for attackers to steal cookies, session tokens, and other sensitive information that could be used to impersonate users or gain unauthorized access to protected resources. The vulnerability is particularly dangerous because it affects multiple versions of Internet Explorer, creating a broad attack surface that could impact millions of users simultaneously.
Security professionals should note that this vulnerability aligns with CWE-79, which specifically addresses cross-site scripting flaws in web applications, and maps to ATT&CK technique T1059.001 for command and scripting interpreter. The bypass mechanism operates through the manipulation of browser security policies, making it particularly challenging to detect and prevent through traditional network monitoring approaches. Organizations should prioritize immediate patching of affected Internet Explorer versions, as Microsoft released security updates to address this specific vulnerability. Additionally, implementing additional security layers such as content security policies, proper input validation, and web application firewalls can provide defense-in-depth measures to mitigate potential exploitation attempts.
The broader implications of this vulnerability highlight the complexity of modern web browser security mechanisms and the challenges of implementing effective XSS protection. It demonstrates that even sophisticated security features can contain implementation flaws that create exploitable conditions, emphasizing the importance of thorough security testing and continuous monitoring. The vulnerability also underscores the critical need for organizations to maintain current security patches and to implement comprehensive security awareness training to help users recognize and avoid potentially malicious web content that could exploit such flaws.