CVE-2016-4583 in tvOS
Summary
by MITRE
WebKit in Apple iOS before 9.3.3, Safari before 9.1.2, and tvOS before 9.2.2 allows remote attackers to bypass the Same Origin Policy and obtain image date from an unintended web site via a timing attack involving an SVG document.
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Analysis
by VulDB Data Team • 09/06/2022
This vulnerability resides in the WebKit rendering engine component of Apple's mobile and desktop operating systems, specifically affecting iOS versions prior to 9.3.3, Safari versions prior to 9.1.2, and tvOS versions prior to 9.2.2. The flaw represents a critical security weakness that undermines the fundamental Same Origin Policy (SOP) enforcement mechanisms that govern web browser security. The vulnerability operates through a sophisticated timing attack vector that exploits the way browsers handle image loading and rendering operations. Attackers can craft malicious SVG documents that leverage timing discrepancies in how different browsers process image data, allowing them to infer and extract sensitive image content from cross-origin domains that should normally be restricted by the browser's security model.
The technical implementation of this vulnerability involves exploiting the timing differences in how browsers load and render image resources across different origins. When a malicious SVG document attempts to load images from different domains, the timing variations in network requests and image processing create observable differences that can be measured and analyzed by an attacker. This timing-based information leakage enables the extraction of image data from unintended web sites, effectively bypassing the SOP that normally prevents such cross-origin data access. The vulnerability specifically targets the image loading behavior within SVG documents, where the asynchronous nature of resource loading creates measurable timing variations that can be weaponized. This attack pattern aligns with CWE-203, which addresses "Information Exposure Through Timing Discrepancies," and demonstrates how seemingly benign timing variations in resource handling can create significant security implications.
The operational impact of this vulnerability extends beyond simple information disclosure, as it represents a sophisticated bypass of browser security boundaries that could enable more advanced attacks. An attacker could potentially reconstruct sensitive image data from cross-origin sources, including user profile pictures, security images, or other potentially sensitive visual content that should remain protected by SOP mechanisms. The vulnerability's exploitation requires careful crafting of malicious SVG documents and precise timing measurements, but once successful, it provides attackers with access to image data that would normally be restricted. This capability could be leveraged in conjunction with other attacks to build more comprehensive reconnaissance profiles of users or systems. The vulnerability also highlights the challenges in implementing robust security policies when dealing with complex rendering engines that handle multiple media types with varying processing requirements.
Mitigation strategies for this vulnerability require immediate system updates to the patched versions of affected Apple operating systems, as the fix addresses the underlying timing discrepancies in image loading and rendering operations. Organizations should ensure that all affected devices are updated to iOS 9.3.3, Safari 9.1.2, or tvOS 9.2.2 respectively, as these versions contain patches that eliminate the timing attack vectors. Additionally, network administrators should consider implementing additional monitoring for suspicious SVG content and timing-based access patterns that could indicate exploitation attempts. The fix likely involves modifying how browsers handle asynchronous image loading operations to ensure consistent timing regardless of cross-origin resource access, thereby eliminating the information leakage channel. This vulnerability demonstrates the importance of considering timing-based side channels in security design and aligns with ATT&CK technique T1059.007 for "Command and Scripting Interpreter: JavaScript' where attackers might leverage similar timing-based information leakage techniques to bypass security controls.