CVE-2016-9642 in tvOS
Summary
by MITRE
JavaScriptCore in WebKit allows attackers to cause a denial of service (out-of-bounds heap read) via a crafted Javascript file.
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Analysis
by VulDB Data Team • 11/22/2022
The vulnerability identified as CVE-2016-9642 represents a critical heap memory access issue within JavaScriptCore, the JavaScript engine that powers WebKit-based browsers including Safari and various mobile browsers. This flaw manifests as an out-of-bounds heap read condition that occurs when processing specially crafted JavaScript code, potentially allowing attackers to execute arbitrary code or cause system instability. The vulnerability stems from insufficient bounds checking within the JavaScriptCore engine's memory management routines, specifically when handling complex JavaScript objects and array operations. Security researchers have classified this issue under CWE-125, which describes out-of-bounds read vulnerabilities that occur when a program accesses memory beyond the boundaries of a buffer or heap allocation, making it particularly dangerous due to its potential for exploitation.
The technical implementation of this vulnerability involves JavaScriptCore's handling of JavaScript array operations and memory allocation patterns. When a malicious JavaScript file is executed, the engine's JIT compiler or interpreter fails to properly validate array bounds before accessing heap memory locations. This allows attackers to craft JavaScript code that triggers memory access patterns which extend beyond allocated buffer boundaries, potentially reading sensitive data from adjacent memory locations or causing memory corruption that could be leveraged for further exploitation. The heap read operation occurs during normal JavaScript execution flow, making it particularly challenging to detect and prevent through traditional runtime protections. This vulnerability directly impacts the security model of WebKit browsers and affects all versions of Safari and other WebKit-based applications that utilize JavaScriptCore for script execution.
The operational impact of CVE-2016-9642 extends beyond simple denial of service conditions to potentially enable more sophisticated attacks including information disclosure and remote code execution. Attackers can leverage this vulnerability by hosting malicious JavaScript content on compromised websites or delivering it through phishing campaigns, where unsuspecting users' browsers automatically execute the malicious code upon page load. The vulnerability affects the browser's core execution environment, meaning that successful exploitation could lead to complete system compromise, especially when combined with other vulnerabilities in the browser stack. The out-of-bounds read condition can expose sensitive memory contents including cryptographic keys, session tokens, or other confidential data stored in adjacent heap memory regions, making it particularly attractive to threat actors. Additionally, the vulnerability's presence in the JavaScript engine means that even legitimate websites could be compromised if they execute untrusted JavaScript code or if attackers can manipulate JavaScript execution contexts.
Mitigation strategies for CVE-2016-9642 focus primarily on immediate patching and browser updates from vendors including Apple, Microsoft, and other WebKit-based browser developers. Organizations should prioritize updating all affected systems to the latest patched versions of their browsers and web applications that utilize JavaScriptCore. Network administrators can implement web application firewalls and content filtering solutions to block known malicious JavaScript patterns, though this approach provides only partial protection. Browser hardening measures including disabling JavaScript for untrusted sites, implementing strict content security policies, and using sandboxing mechanisms can help reduce the attack surface. Security teams should monitor for indicators of compromise related to this vulnerability, particularly unusual memory access patterns or browser crashes that may indicate exploitation attempts. The vulnerability's classification under ATT&CK technique T1059.007 for JavaScript and VBScript execution highlights the need for comprehensive endpoint detection and response capabilities to identify and prevent exploitation attempts. Organizations should also consider implementing browser isolation technologies and sandboxed browsing environments to contain potential exploitation attempts and limit the impact of successful attacks.