CVE-2015-5860 in iOS
Summary
by MITRE
The CFNetwork HTTPProtocol component in Apple iOS before 9 mishandles HSTS state, which allows remote attackers to bypass the Safari private-browsing protection mechanism and track users via a crafted web site.
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Analysis
by VulDB Data Team • 11/21/2024
The vulnerability identified as CVE-2015-5860 resides within Apple iOS versions prior to 9.0, specifically affecting the CFNetwork HTTPProtocol component that handles Hypertext Transfer Protocol operations. This flaw represents a significant security oversight in how the operating system manages HTTP Strict Transport Security state information, creating a pathway for malicious actors to circumvent privacy protections designed to safeguard user browsing activities. The issue directly impacts Safari's private browsing mode functionality, which is intended to prevent tracking through the preservation of user session state and the prevention of persistent cookies.
The technical mechanism behind this vulnerability involves the improper handling of HSTS state management within the CFNetwork framework. When a user navigates to a website that implements HSTS, the system should maintain strict adherence to the security policy that enforces secure connections. However, in affected iOS versions, the system fails to properly maintain HSTS state across different browsing sessions or contexts, particularly when transitioning between regular and private browsing modes. This mismanagement allows attackers to craft malicious websites that can detect whether a user has previously visited specific sites, effectively creating a tracking mechanism that undermines the privacy guarantees of private browsing.
The operational impact of this vulnerability extends beyond simple privacy concerns to encompass broader security implications for user data protection and online anonymity. Attackers can exploit this weakness to perform user tracking across different browsing sessions, potentially linking private browsing activities with regular browsing patterns to reconstruct user behavior profiles. This tracking capability undermines the fundamental purpose of private browsing modes and creates opportunities for targeted advertising, surveillance, or even more sophisticated attack vectors that rely on user behavior patterns. The vulnerability specifically targets the Safari browser's private browsing protection mechanism, which is designed to prevent the storage of cookies, cache data, and other session information that could be used for tracking purposes.
This vulnerability aligns with CWE-352, which addresses Cross-Site Request Forgery (CSRF) and related security flaws, though the specific implementation involves improper state management rather than request manipulation. The flaw also connects to ATT&CK technique T1566, which covers phishing and social engineering attacks that leverage browser vulnerabilities to compromise user privacy. The security implications extend to the broader category of information disclosure vulnerabilities, where proper state management should prevent unauthorized access to user session data. Organizations and users should recognize that this vulnerability represents a failure in the browser's security model to maintain consistent protection mechanisms across different browsing contexts, creating persistent tracking capabilities that persist even when users believe they are operating in private mode.
Mitigation strategies for CVE-2015-5860 primarily involve upgrading to iOS 9.0 or later versions where Apple has implemented proper HSTS state management. Users should also exercise caution when visiting untrusted websites and consider disabling private browsing features if they require maximum security protection. Network administrators should monitor for affected systems and ensure timely deployment of security updates. The vulnerability demonstrates the critical importance of maintaining proper state management in security-sensitive components and highlights the need for comprehensive testing of privacy protection mechanisms across different operating environments and user contexts.