CVE-2016-4760 in iOS
Summary
by MITRE
WebKit in Apple iOS before 10, iTunes before 12.5.1 on Windows, and Safari before 10 allows remote attackers to conduct DNS rebinding attacks against non-HTTP Safari sessions by leveraging HTTP/0.9 support.
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Analysis
by VulDB Data Team • 09/20/2022
The vulnerability described in CVE-2016-4760 represents a significant security flaw in Apple's WebKit rendering engine that affected multiple platforms including iOS versions prior to 10, iTunes versions before 12.5.1 on Windows, and Safari versions before 10. This issue stems from the improper handling of HTTP/0.9 protocol support within the WebKit framework, creating a pathway for sophisticated DNS rebinding attacks that can bypass traditional security boundaries. The vulnerability specifically targets non-HTTP Safari sessions, making it particularly dangerous as it exploits the underlying network communication mechanisms that are typically considered secure.
The technical flaw manifests through WebKit's support for HTTP/0.9 protocol, which is an early version of the HTTP specification that lacks many of the security features present in modern HTTP implementations. When WebKit processes HTTP/0.9 requests, it fails to properly validate or restrict DNS resolution behavior, allowing attackers to manipulate DNS responses during the session establishment process. This creates a window where malicious actors can redirect traffic from legitimate domains to internal network resources, effectively bypassing the same-origin policy and other security restrictions that normally protect users from internal network attacks. The vulnerability operates through a DNS rebinding attack vector that leverages the timing and resolution characteristics of HTTP/0.9 connections to establish unauthorized access to local network services.
The operational impact of this vulnerability is substantial as it enables remote attackers to conduct sophisticated attacks against users' local networks without requiring any special privileges or physical access to the target system. Attackers can exploit this weakness to gain access to internal network services, devices, and resources that would normally be protected by firewalls and network segmentation. The attack can be particularly dangerous in corporate environments where users may be browsing malicious websites while connected to internal networks, potentially allowing attackers to access sensitive internal systems, printers, cameras, or other networked devices. This vulnerability essentially transforms a web browser into a tool for network reconnaissance and exploitation, making it a critical concern for organizations with robust network security policies.
This vulnerability maps directly to CWE-647, which addresses the use of insecure HTTP versions that lack proper security controls, and aligns with ATT&CK technique T1071.004 for application layer protocol usage. The attack pattern follows the typical DNS rebinding methodology outlined in various security frameworks, where attackers manipulate DNS resolution timing to bypass security boundaries. Organizations should implement immediate mitigations including disabling HTTP/0.9 support in WebKit-based browsers, updating to patched versions of affected software, and implementing network segmentation controls. The recommended remediation strategy involves applying the security patches released by Apple for iOS 10, Safari 10, and iTunes 12.5.1, while also deploying network monitoring solutions to detect suspicious DNS resolution patterns and implementing strict firewall rules to limit access to internal network resources from external web browsing sessions.
The broader implications of this vulnerability highlight the importance of proper protocol handling and the potential risks associated with supporting legacy protocols in modern security contexts. It demonstrates how seemingly minor protocol support features can create significant security holes when not properly integrated with comprehensive security controls. Organizations should conduct thorough security assessments of their WebKit-based applications and ensure that all network communication channels are properly validated and restricted. The vulnerability also emphasizes the need for continuous security monitoring and the importance of staying current with vendor security patches, as this attack vector could be exploited by threat actors to gain unauthorized access to sensitive network resources.