CVE-2016-7281 in Edge
Summary
by MITRE
The Web Workers implementation in Microsoft Internet Explorer 10 and 11 and Microsoft Edge allows remote attackers to bypass the Same Origin Policy via unspecified vectors, aka "Microsoft Browser Security Feature Bypass Vulnerability."
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Analysis
by VulDB Data Team • 10/08/2022
The vulnerability identified as CVE-2016-7281 represents a critical security flaw in Microsoft's web browser implementations that undermines fundamental web security mechanisms. This issue affects Internet Explorer 10 and 11, as well as Microsoft Edge browser versions, specifically targeting the Web Workers functionality that enables background processing in web applications. The vulnerability stems from an insufficient implementation of the Same Origin Policy, which serves as the primary security boundary protecting web resources from cross-origin access attempts. When exploited, this flaw allows remote attackers to circumvent the security controls that normally prevent scripts from different origins from accessing each other's resources, effectively breaking down the isolation mechanisms that keep web applications secure.
The technical nature of this vulnerability lies within the Web Workers API implementation where Microsoft browsers fail to properly enforce origin-based restrictions during cross-origin communication scenarios. Web Workers are designed to run scripts in background threads separate from the main execution thread, enabling parallel processing without blocking the user interface. However, the flawed implementation allows malicious actors to craft attacks that exploit the way these workers handle cross-origin resource requests. The unspecified vectors mentioned in the description suggest that multiple attack paths exist within the Web Workers implementation, potentially including improper handling of cross-origin messages, inadequate sandboxing of worker contexts, or flawed origin validation mechanisms that should prevent unauthorized access to resources from different domains. This represents a classic bypass vulnerability where the security control mechanism itself contains a weakness that allows attackers to circumvent intended protections.
The operational impact of CVE-2016-7281 is significant as it enables attackers to perform cross-origin information disclosure and potentially execute malicious code across different domains. Attackers could leverage this vulnerability to access sensitive data from other origins, including cookies, local storage, and other browser resources that should remain isolated. The consequences extend beyond simple data theft, as this bypass could enable more sophisticated attacks such as cross-site scripting exploitation, session hijacking, or privilege escalation within web applications. The vulnerability affects a broad user base since Internet Explorer 10 and 11 were widely deployed enterprise browsers, while Microsoft Edge represented the newer browser implementation that inherited these security weaknesses. Organizations relying on these browsers for web applications or internal systems would face substantial risk exposure, particularly in environments where users might encounter malicious websites or where web applications handle sensitive information.
This vulnerability aligns with CWE-284, which describes improper access control issues in software implementations, and specifically relates to the improper enforcement of access restrictions that should prevent unauthorized access to resources. From an ATT&CK framework perspective, this vulnerability maps to T1059.001 for command and scripting interpreter execution, T1071.001 for application layer protocol usage, and T1190 for exploit for client execution. The attack surface is particularly concerning given that Web Workers are commonly used in modern web applications, making this vulnerability potentially exploitable across a wide range of legitimate web services. Organizations should implement immediate mitigations including browser updates, network-level restrictions, and enhanced monitoring for suspicious cross-origin communication patterns. The vulnerability highlights the critical importance of proper sandboxing and access control enforcement in browser implementations, particularly for features that operate outside the normal execution context of web pages.
Mitigation strategies should focus on both immediate remediation and long-term architectural improvements. Microsoft released patches addressing this vulnerability through regular security updates, and organizations should ensure all affected browsers are updated to the latest versions. Network administrators should consider implementing content security policies that limit the execution of cross-origin web workers and monitor for anomalous cross-origin communication patterns. The vulnerability also underscores the need for comprehensive browser security testing, particularly for features that operate in background contexts where traditional security controls might not be fully enforced. Additionally, web application developers should validate their applications for proper handling of cross-origin scenarios and consider implementing additional client-side protections against malicious cross-origin attempts. This vulnerability demonstrates that even fundamental browser security features require continuous scrutiny and updating to maintain their effectiveness against evolving attack techniques.