CVE-2016-1786 in iOS
Summary
by MITRE
The Page Loading implementation in WebKit in Apple iOS before 9.3 and Safari before 9.1 mishandles HTTP responses with a 3xx (aka redirection) status code, which allows remote attackers to spoof the displayed URL, bypass the Same Origin Policy, and obtain sensitive cached information via a crafted web site.
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Analysis
by VulDB Data Team • 07/11/2022
The vulnerability identified as CVE-2016-1786 resides within the WebKit rendering engine implementation in Apple iOS versions prior to 9.3 and Safari versions before 9.1. This flaw specifically affects how the browser handles HTTP redirect responses with 3xx status codes during page loading operations. The issue stems from improper validation and processing of these redirection responses, creating a security gap that can be exploited by remote attackers to manipulate the browser's URL display and access mechanisms.
The technical implementation flaw involves the browser's failure to properly validate the chain of redirects when processing 3xx responses. When a web server returns a redirection response, the browser should maintain proper tracking of the original URL while displaying the final destination. However, in affected versions, WebKit's page loading mechanism fails to correctly manage this process, allowing attackers to craft malicious websites that can manipulate the URL bar display while maintaining access to cached resources from the original domain. This misimplementation creates a situation where the browser's user interface misleadingly presents one URL while internally maintaining access to resources from another, effectively bypassing the Same Origin Policy enforcement mechanisms that protect against cross-site scripting attacks.
The operational impact of this vulnerability extends beyond simple URL spoofing, as it enables attackers to access sensitive cached information from the original domain. This cached data may include session cookies, authentication tokens, or other sensitive user data that should normally be restricted based on the same origin policy. The attack vector involves a malicious website that triggers a redirect chain, causing the browser to display a legitimate-looking URL while maintaining access to cached resources from the targeted domain. This creates a potential for credential theft, session hijacking, and other attacks that exploit the trust relationship between the browser and the user.
From a cybersecurity perspective, this vulnerability aligns with CWE-200, which addresses information exposure, and represents a specific case of improper input validation in web application security. The attack pattern corresponds to techniques documented in the ATT&CK framework under T1056.001 for credential access through web applications. The vulnerability demonstrates a classic case of a trust boundary violation where the browser's display mechanism becomes decoupled from its security enforcement mechanisms, creating a scenario where user-perceived security context differs from actual security state. Organizations should prioritize patching affected systems to ensure proper redirect handling and maintain the integrity of the same origin policy enforcement. The mitigation strategy requires immediate deployment of iOS 9.3 and Safari 9.1 updates, which correct the redirect processing logic and restore proper URL display behavior while maintaining security boundaries.