CVE-2015-3763 in iOS
Summary
by MITRE
Safari in Apple iOS before 8.4.1 does not limit the rate of JavaScript alert messages, which allows remote attackers to cause a denial of service (apparent browser locking) via a crafted web site.
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Analysis
by VulDB Data Team • 06/10/2022
The vulnerability identified as CVE-2015-3763 represents a significant denial of service weakness in Apple iOS Safari browsers prior to version 8.4.1. This flaw stems from the browser's inadequate rate limiting mechanisms for JavaScript alert dialogues, creating a scenario where malicious web content can overwhelm the user interface with rapid-fire alert messages. The issue manifests when a crafted website triggers numerous JavaScript alert calls in quick succession, leading to the browser becoming unresponsive and effectively locking the user interface. From a cybersecurity perspective, this vulnerability demonstrates how seemingly benign browser features can be exploited to create operational disruptions that compromise user experience and system availability.
The technical implementation of this vulnerability resides in the JavaScript execution engine's handling of alert dialogues within the Safari browser environment. When a web page invokes the alert() function repeatedly without proper rate limiting, the browser's user interface becomes flooded with dialog boxes that cannot be dismissed quickly enough. This creates a cascading effect where each alert message consumes system resources and blocks further user interaction with the browser interface. The flaw specifically affects iOS versions before 8.4.1, indicating that Apple had not yet implemented sufficient throttling mechanisms to prevent excessive alert generation. This issue maps directly to CWE-704 in the Common Weakness Enumeration, which categorizes it as a weakness related to insufficient resource management and inadequate input validation in web browser contexts.
The operational impact of CVE-2015-3763 extends beyond simple user inconvenience to represent a genuine denial of service threat that can affect productivity and system usability. When exploited, the vulnerability causes the Safari browser to become completely unresponsive, forcing users to either wait for the alerts to clear or restart the browser application entirely. Attackers can leverage this weakness in various attack scenarios including phishing campaigns, malicious advertising networks, or targeted attacks against specific user groups. The vulnerability aligns with several ATT&CK framework techniques, particularly those related to resource exhaustion and user interface manipulation, as it exploits the browser's interface handling mechanisms to create operational disruption. This type of attack can be particularly effective in enterprise environments where users may be browsing untrusted websites or where automated browser interactions could compound the denial of service effect.
Mitigation strategies for this vulnerability primarily involve upgrading to Apple iOS version 8.4.1 or later, which includes proper rate limiting for JavaScript alert messages. System administrators should implement comprehensive mobile device management policies that ensure all iOS devices receive timely security updates. Network-level defenses can include web content filtering solutions that detect and block suspicious alert-heavy web pages, though this approach may impact legitimate website functionality. Browser security configurations should also include disabling JavaScript when possible, as this prevents the execution of alert-based attacks entirely. Organizations should conduct regular security assessments to identify potentially vulnerable iOS devices within their networks and implement patch management procedures that prioritize critical browser security updates. The vulnerability serves as a reminder of the importance of proper input validation and resource management in browser implementations, particularly when dealing with user-facing interface elements that can be easily abused through automated scripting.