CVE-2015-6144 in Internet Explorer
Summary
by MITRE
Microsoft Internet Explorer 8 through 11 and Microsoft Edge mishandle HTML attributes in HTTP responses, which allows remote attackers to bypass a cross-site scripting (XSS) protection mechanism via unspecified vectors, aka "Microsoft Browser XSS Filter Bypass Vulnerability."
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Analysis
by VulDB Data Team • 06/28/2022
The vulnerability identified as CVE-2015-6144 represents a critical flaw in Microsoft's web browser security mechanisms that affects Internet Explorer versions 8 through 11 and Microsoft Edge. This issue stems from the improper handling of HTML attributes within HTTP responses, creating a pathway for malicious actors to circumvent the built-in cross-site scripting protection measures that browsers typically employ to safeguard users from malicious code injection attacks. The vulnerability operates at the intersection of web application security and browser implementation, where the XSS filter mechanism fails to properly validate or sanitize HTML attributes received in HTTP response headers, allowing attackers to craft malicious payloads that bypass these protective measures.
The technical implementation of this vulnerability involves the manipulation of HTTP response headers that contain HTML attributes, specifically those that might be interpreted by the browser's XSS filter as legitimate content. When browsers process these headers, they may incorrectly parse or ignore certain HTML attribute specifications, leading to a scenario where malicious scripts can be executed in the context of a user's session without triggering the expected security warnings. This bypass occurs because the browser's security mechanisms do not adequately account for all possible variations in how HTML attributes might be transmitted or interpreted within HTTP responses, creating a gap in the defensive framework that should protect against cross-site scripting attacks. The flaw demonstrates a classic weakness in input validation and sanitization where the security system fails to properly parse edge cases in HTML attribute handling.
The operational impact of CVE-2015-6144 extends beyond simple script execution, as it allows attackers to perform sophisticated phishing attacks, session hijacking, and data exfiltration operations against users of vulnerable browsers. When successful, this vulnerability enables attackers to inject malicious scripts that can steal cookies, redirect users to malicious sites, or perform actions on behalf of authenticated users without their knowledge. The attack vector typically involves crafting HTTP responses that contain specially formatted HTML attributes designed to exploit the parsing inconsistencies in the browser's XSS filter, making this vulnerability particularly dangerous in environments where users interact with untrusted web content. Security researchers have categorized this issue under CWE-79 as a cross-site scripting vulnerability, while threat actors have mapped it to ATT&CK technique T1059.001 for command and scripting interpreter usage, highlighting the potential for these bypasses to enable further exploitation.
Mitigation strategies for this vulnerability require immediate patch deployment through Microsoft's regular security updates, as the flaw exists within the core browser functionality and cannot be effectively addressed through client-side configuration changes alone. Organizations should implement comprehensive browser update policies that ensure all users maintain current versions of Microsoft Edge and Internet Explorer, while also considering the deployment of additional security layers such as content security policies and web application firewalls to provide defense-in-depth. Security teams must also conduct thorough vulnerability assessments to identify potentially affected systems and monitor network traffic for indicators of exploitation attempts. The vulnerability underscores the importance of maintaining up-to-date browser security implementations and highlights the critical need for continuous security testing of browser security mechanisms to identify and remediate similar bypass vulnerabilities before they can be exploited by malicious actors in the wild.