CVE-2017-2492 in tvOS
Summary
by MITRE
An issue was discovered in certain Apple products. iOS before 10.3 is affected. Safari before 10.1 is affected. tvOS before 10.2 is affected. The issue involves the "JavaScriptCore" component. It allows remote attackers to conduct Universal XSS (UXSS) attacks via a crafted web site that triggers prototype mishandling.
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Analysis
by VulDB Data Team • 01/20/2020
The vulnerability identified as CVE-2017-2492 represents a critical security flaw within Apple's JavaScriptCore engine that affects multiple operating systems and applications. This issue specifically targets iOS versions prior to 10.3, Safari versions prior to 10.1, and tvOS versions prior to 10.2, demonstrating the widespread impact across Apple's ecosystem. The vulnerability resides within the JavaScriptCore component which serves as the core JavaScript engine powering web content in Apple's browsers and applications, making it a prime target for sophisticated exploitation techniques.
The technical flaw manifests through prototype mishandling within the JavaScriptCore engine, creating a condition where remote attackers can craft malicious websites designed to exploit this vulnerability. This prototype manipulation allows attackers to bypass standard security mechanisms and execute malicious code in the context of the victim's browser session. The vulnerability is classified as a Universal XSS (UXSS) attack vector, which means that the exploit can work across different browser contexts and potentially bypass traditional cross-site scripting protections that rely on sandboxing mechanisms. This particular weakness stems from improper handling of JavaScript object prototypes, allowing attackers to manipulate the prototype chain in ways that should not be permitted.
The operational impact of this vulnerability is severe as it enables remote code execution capabilities without requiring user interaction beyond visiting a malicious website. This makes it particularly dangerous for targeted attacks where adversaries can deliver payloads through compromised websites, email attachments, or malicious advertisements. The vulnerability allows attackers to execute arbitrary code with the privileges of the victim's browser session, potentially leading to complete system compromise, data theft, or further lateral movement within networks. The UXSS nature of this vulnerability means that traditional security measures such as content security policies and sandboxing may be insufficient to prevent exploitation, as the attack can leverage the browser's own JavaScript engine against itself.
The vulnerability aligns with CWE-471, which describes the weakness of "Modification of Externally-Contained Data" and relates to the improper handling of prototype objects in JavaScript environments. From an ATT&CK framework perspective, this vulnerability maps to T1059.007 for JavaScript execution and T1211 for exploitation of a remote service, with potential for T1078 for legitimate credentials use if the attack succeeds in compromising user sessions. The attack requires minimal user interaction beyond visiting a malicious website, making it particularly effective for phishing campaigns and drive-by downloads. Organizations should implement immediate mitigation strategies including updating to patched versions of affected Apple products, implementing web application firewalls, and monitoring for suspicious web traffic patterns that may indicate exploitation attempts.
Mitigation strategies for CVE-2017-2492 should prioritize immediate deployment of Apple's security patches for iOS 10.3, Safari 10.1, and tvOS 10.2, as these releases contain the necessary fixes for the prototype handling issues within JavaScriptCore. Network administrators should consider implementing browser hardening measures such as disabling JavaScript for untrusted sites, implementing content security policies, and deploying intrusion detection systems that can identify exploitation attempts. Additionally, user education regarding the dangers of visiting untrusted websites and the importance of keeping software updated remains crucial in defending against this class of vulnerability. Regular security assessments should include verification that affected systems have been properly patched and that no legacy versions remain in use within the organization's infrastructure.