CVE-2015-3753 in Safari
Summary
by MITRE
WebKit in Apple Safari before 6.2.8, 7.x before 7.1.8, and 8.x before 8.0.8, as used in iOS before 8.4.1 and other products, does not properly perform taint checking for CANVAS elements, which allows remote attackers to bypass the Same Origin Policy and obtain sensitive image data by leveraging a redirect to a data:image resource.
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Analysis
by VulDB Data Team • 11/24/2024
The vulnerability described in CVE-2015-3753 represents a critical security flaw in Apple WebKit's implementation of canvas element taint checking mechanisms. This issue affects multiple versions of Safari and iOS, specifically targeting the browser's ability to enforce the Same Origin Policy when processing canvas elements. The vulnerability stems from insufficient validation of data:image resources that can be manipulated through redirects, creating a pathway for attackers to bypass fundamental web security boundaries.
The technical flaw manifests in WebKit's failure to properly validate the origin of image data when rendering canvas elements. When a web page attempts to draw an image onto a canvas element, the browser should perform taint checking to ensure that the image originates from the same domain as the requesting page. However, in the affected versions, this validation mechanism can be circumvented through carefully crafted redirects that point to data:image resources. This allows malicious actors to exploit the vulnerability by redirecting canvas operations to controlled data URLs that contain sensitive information from other origins.
The operational impact of this vulnerability extends beyond simple data theft, as it fundamentally undermines the browser's security model. Attackers can leverage this flaw to extract sensitive image data from different origins, potentially accessing private user information, authentication tokens, or other confidential data that should be protected by the Same Origin Policy. The vulnerability affects a wide range of Apple products including iOS versions before 8.4.1, making it particularly dangerous as it impacts mobile users who may be accessing malicious websites through various application contexts. This type of cross-origin data leakage can enable more sophisticated attacks including credential harvesting, session hijacking, and information disclosure that can compromise user privacy and system integrity.
This vulnerability maps directly to CWE-200, which addresses the exposure of sensitive information, and aligns with ATT&CK technique T1071.001 for application layer protocol. The flaw represents a classic case of insufficient input validation combined with improper access control mechanisms. Security researchers have noted that such taint checking failures in canvas implementations are particularly concerning because they can be exploited through seemingly benign web interactions. The vulnerability's impact is amplified by the fact that it affects widely used browser software and mobile operating systems, making it a prime target for exploitation in targeted attacks. Organizations should implement immediate mitigations including updating to patched versions of Safari and iOS, implementing network-level controls to monitor for suspicious redirect patterns, and conducting security assessments to identify potential exploitation attempts. The incident highlights the critical importance of proper taint checking mechanisms in web browsers and the necessity of rigorous security testing for core browser components that handle sensitive data processing operations.