CVE-2015-3754 in Safari
Summary
by MITRE
The private-browsing implementation in WebKit in Apple Safari before 6.2.8, 7.x before 7.1.8, and 8.x before 8.0.8 does not prevent caching of HTTP authentication credentials, which makes it easier for remote attackers to track users via a crafted web site.
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Analysis
by VulDB Data Team • 06/09/2022
The vulnerability identified as CVE-2015-3754 resides within the WebKit rendering engine's implementation of private browsing mode in Apple Safari browsers across multiple versions. This flaw represents a critical security oversight that undermines the fundamental privacy protections users expect when engaging in private browsing sessions. The issue specifically affects Safari versions prior to 6.2.8, 7.1.8, and 8.0.8, where the browser's private browsing functionality fails to properly isolate sensitive authentication data from standard caching mechanisms. The vulnerability operates at the intersection of web browser security architecture and user privacy expectations, creating a scenario where malicious actors can exploit the inconsistent handling of authentication credentials.
The technical flaw manifests in how WebKit processes HTTP authentication credentials during private browsing sessions. Normally, private browsing modes should maintain strict separation between private and public data, ensuring that sensitive information such as authentication tokens and credentials do not persist in caches or temporary storage areas. However, this vulnerability allows HTTP authentication credentials to be cached even when users believe they are operating in a private browsing context. The flaw specifically affects the caching behavior of authentication data, enabling persistent storage of credentials that should remain ephemeral. This technical deficiency stems from improper isolation of private browsing state from standard browser caching mechanisms, creating a persistent data leak that violates fundamental privacy assumptions.
The operational impact of this vulnerability extends beyond simple credential exposure to create sophisticated tracking capabilities for remote attackers. When a malicious website crafts specific HTTP authentication challenges, the cached credentials can be leveraged to establish persistent user identification across different browsing sessions. This tracking mechanism operates through cache-based fingerprinting where attackers can correlate cached authentication data with user behavior patterns, effectively bypassing privacy protections that users rely upon. The vulnerability enables what security researchers classify as cross-session tracking, where user activities can be monitored and correlated over time without explicit user knowledge or consent. This capability directly violates user privacy expectations and creates opportunities for targeted surveillance and behavioral analysis.
The vulnerability aligns with CWE-200, which addresses "Information Exposure," and demonstrates how inadequate privacy controls can create persistent data leakage scenarios. From an ATT&CK framework perspective, this vulnerability maps to techniques involving credential access and tracking activities, specifically targeting the T1566.002 sub-technique related to credential access through web browsers. The attack vector requires a crafted website that can trigger HTTP authentication challenges, making it particularly dangerous in phishing scenarios or malicious web applications. Security professionals categorize this as a privacy violation that undermines user trust in browser security models and demonstrates the critical importance of proper isolation between different browser states and data handling mechanisms.
Mitigation strategies for this vulnerability require immediate patching of affected Safari versions to ensure proper isolation of authentication credentials during private browsing sessions. Organizations should implement comprehensive browser security policies that include regular updates and monitoring for similar vulnerabilities. Users must be educated about the risks associated with private browsing modes and the importance of keeping browsers current with security patches. The vulnerability highlights the necessity of robust testing for privacy-related features and the importance of maintaining consistent security boundaries between different browser states. Security teams should monitor for similar issues in other browser implementations and ensure that caching mechanisms properly respect user privacy settings and browsing context requirements.