CVE-2015-6981 in iOS
Summary
by MITRE
WebKit, as used in Apple iOS before 9.1, allows remote attackers to execute arbitrary code or cause a denial of service (memory corruption and application crash) via a crafted web site, a different vulnerability than other WebKit CVEs listed in APPLE-SA-2015-10-21-1.
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Analysis
by VulDB Data Team • 06/24/2022
CVE-2015-6981 represents a critical memory corruption vulnerability within WebKit's JavaScriptCore engine that affected Apple iOS versions prior to 9.1. This vulnerability stems from improper handling of memory allocation and deallocation during JavaScript execution, creating opportunities for remote code execution through malicious web content. The flaw specifically manifests when WebKit processes crafted JavaScript code that triggers heap corruption, allowing attackers to manipulate memory pointers and execute arbitrary instructions. The vulnerability operates at the intersection of multiple security domains including memory safety, JavaScript engine architecture, and mobile operating system security boundaries.
The technical implementation of this vulnerability involves a use-after-free condition within WebKit's garbage collection mechanisms, where objects are freed from memory but references to them persist in the JavaScript execution context. This creates a scenario where subsequent memory allocation can overwrite the freed object's memory space, enabling attackers to inject malicious code into the execution flow. The flaw is particularly dangerous because it operates within the browser's sandboxed environment, yet allows privilege escalation through memory corruption techniques that bypass traditional security boundaries. This vulnerability aligns with CWE-416, Use After Free, and CWE-122, Heap Overflow, demonstrating the intersection of memory management errors that can lead to arbitrary code execution.
Operationally, this vulnerability exposes iOS users to significant risk through drive-by download attacks where simply visiting a compromised website can result in full system compromise. The attack vector requires no user interaction beyond navigation to the malicious site, making it particularly dangerous for mobile environments where users frequently browse untrusted content. The vulnerability can be exploited to execute malicious payloads that may include malware installation, data exfiltration, or persistent backdoor establishment. Attackers can leverage this flaw to gain unauthorized access to sensitive user information, including personal data, communications, and device credentials, with implications extending beyond individual privacy to potential corporate security breaches.
Mitigation strategies for CVE-2015-6981 require immediate patching of affected iOS versions to 9.1 or later, where Apple implemented memory safety improvements and enhanced heap management within JavaScriptCore. Organizations should deploy network-based intrusion detection systems that can identify and block known malicious web content associated with exploitation attempts. Mobile device management solutions should enforce automatic update policies to ensure all iOS devices receive security patches promptly. Additionally, users should avoid visiting untrusted websites and maintain awareness of phishing attempts that may leverage this vulnerability. Security professionals should monitor threat intelligence feeds for exploitation attempts and consider implementing browser hardening measures such as disabling unnecessary JavaScript features and employing content security policies to limit potential attack surface. The vulnerability demonstrates the critical importance of maintaining up-to-date mobile security patches and highlights the need for robust memory safety practices in browser engine implementations.