CVE-2016-1785 in iOS
Summary
by MITRE
The Page Loading implementation in WebKit in Apple iOS before 9.3 and Safari before 9.1 mishandles character encoding during access to cached data, which allows remote attackers to bypass the Same Origin Policy and obtain sensitive information via a crafted web site.
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Analysis
by VulDB Data Team • 07/11/2022
The vulnerability identified as CVE-2016-1785 represents a critical security flaw in the WebKit rendering engine that powers Apple iOS and Safari browsers. This issue specifically affects versions prior to iOS 9.3 and Safari 9.1, where the page loading implementation demonstrates improper handling of character encoding when accessing cached data. The flaw resides in how WebKit processes and manages cached resources, creating a pathway for malicious actors to exploit the browser's security mechanisms. The vulnerability is particularly concerning because it directly undermines the fundamental Same Origin Policy that serves as a cornerstone of web security architecture, effectively allowing unauthorized data access between different origins.
The technical implementation of this vulnerability stems from WebKit's cache management system failing to properly validate character encoding when retrieving previously cached web resources. When a browser encounters cached content, it typically maintains strict boundaries regarding the origin from which resources were fetched to prevent cross-origin data leakage. However, in affected versions, the character encoding handling mechanism becomes compromised during cache retrieval operations, enabling attackers to manipulate the encoding process in a way that bypasses these security restrictions. This improper encoding handling creates a condition where cached resources from one origin can be accessed or interpreted in a manner that reveals sensitive information to unauthorized domains.
The operational impact of this vulnerability extends beyond simple information disclosure, as it fundamentally weakens the browser's security model. Attackers can craft malicious websites that exploit this flaw to access cached data from other origins, potentially obtaining session cookies, authentication tokens, or other sensitive information that should remain protected by the Same Origin Policy. This type of cross-origin information leakage can lead to session hijacking, credential theft, and unauthorized access to user accounts across different web applications. The vulnerability is particularly dangerous in environments where users frequently access multiple web applications, as cached data from one application could be leveraged to compromise others.
This vulnerability aligns with CWE-200, which addresses "Information Exposure," and represents a specific implementation weakness in how cached data is processed and validated. From an ATT&CK framework perspective, this flaw maps to techniques involving credential access and information gathering, specifically targeting the browser's security boundaries. The vulnerability demonstrates a classic case of insufficient input validation and improper resource handling that allows for privilege escalation through cache manipulation. Security researchers have noted that such flaws often emerge from complex interactions between caching mechanisms and character encoding systems, where the interaction between these components creates unexpected security boundaries. Organizations should prioritize patching affected systems immediately, as the vulnerability provides attackers with a straightforward method to bypass core web security protections. The fix implemented by Apple in iOS 9.3 and Safari 9.1 involved strengthening the character encoding validation process during cache access operations, ensuring that cached data cannot be accessed across origin boundaries without proper authorization.