CVE-2015-3750 in Safari
Summary
by MITRE
WebKit in Apple Safari before 6.2.8, 7.x before 7.1.8, and 8.x before 8.0.8, as used in iOS before 8.4.1 and other products, does not enforce the HTTP Strict Transport Security (HSTS) protection mechanism for Content Security Policy (CSP) report requests, which allows man-in-the-middle attackers to obtain sensitive information by sniffing the network or spoof a report by modifying the client-server data stream.
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Analysis
by VulDB Data Team • 06/09/2022
The vulnerability described in CVE-2015-3750 represents a critical security flaw in Apple Safari's WebKit implementation that undermines fundamental web security protections. This issue affects multiple versions of Safari across different operating systems including iOS, macOS, and various web browsers that utilize WebKit as their rendering engine. The flaw specifically targets the interaction between HTTP Strict Transport Security and Content Security Policy mechanisms, creating a dangerous gap in the security architecture that malicious actors can exploit to compromise user data and communications.
The technical root cause of this vulnerability lies in Safari's failure to properly enforce HSTS protection for Content Security Policy report requests. When a web application implements CSP policies to monitor and report on security violations, these reports are typically sent back to the server for analysis and logging. However, in affected versions of Safari, the browser does not ensure that these CSP report requests are transmitted over secure HTTPS connections even when the originating website has properly configured HSTS headers. This omission creates a window of opportunity for attackers to intercept these sensitive reports or modify them during transit, effectively bypassing the intended security controls.
The operational impact of this vulnerability extends beyond simple data interception, as it fundamentally compromises the integrity of security monitoring systems. Attackers can leverage this weakness to perform man-in-the-middle attacks that allow them to capture sensitive information contained within CSP violation reports, which may include details about web application vulnerabilities, user behavior patterns, and potentially even authentication tokens or session information. The ability to spoof these reports also means that attackers can manipulate the security monitoring data to hide malicious activities or create false positives that could confuse security teams during incident response.
This vulnerability aligns with CWE-319, which specifically addresses the improper handling of sensitive data over insecure channels, and represents a significant deviation from the expected behavior outlined in the HTTP Strict Transport Security specification. The issue demonstrates how seemingly isolated security mechanisms can interact in unexpected ways to create broader security weaknesses. From an ATT&CK framework perspective, this vulnerability enables techniques such as credential access through network sniffing and defense evasion by manipulating security monitoring data, making it particularly dangerous in enterprise environments where CSP monitoring is commonly deployed.
Organizations and users affected by this vulnerability should immediately update to the patched versions of Safari and iOS that properly enforce HSTS for CSP report requests. The mitigation strategy involves ensuring that all web applications implementing CSP policies are configured to use secure connections for reporting and that network monitoring systems are updated to detect potential manipulation of security reports. Additionally, security teams should review their existing CSP policies to ensure they are not inadvertently exposing sensitive information through insecure reporting mechanisms, and consider implementing additional monitoring for unusual patterns in CSP violation reports that might indicate active exploitation attempts.