CVE-2012-0642 in iOS
Summary
by MITRE
Integer underflow in Apple iOS before 5.1 allows remote attackers to execute arbitrary code or cause a denial of service (device crash) via a crafted catalog file in an HFS disk image.
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Analysis
by VulDB Data Team • 03/21/2021
The vulnerability identified as CVE-2012-0642 represents a critical integer underflow flaw within Apple iOS versions prior to 5.1 that specifically affects the handling of HFS disk images. This vulnerability resides in the operating system's file system parsing mechanisms and demonstrates a classic software security weakness that can be exploited remotely to achieve arbitrary code execution or system compromise. The flaw occurs when the iOS operating system processes crafted catalog files embedded within HFS disk images, creating conditions where integer arithmetic operations produce unexpectedly small values that can be exploited by malicious actors. Such vulnerabilities are particularly dangerous because they can be triggered through seemingly benign file operations and do not require user interaction beyond the simple act of mounting or accessing the malicious disk image.
The technical nature of this vulnerability aligns with CWE-191, which specifically addresses integer underflow conditions where a computation results in a value that is smaller than the minimum value that can be represented by the data type. In the context of iOS file system processing, this occurs when the system attempts to calculate offsets or sizes within HFS catalog structures, and an integer underflow allows attackers to manipulate memory pointers or buffer boundaries. The flaw manifests when the system fails to properly validate the bounds of integer calculations used for parsing disk image metadata, particularly within the HFS catalog file structure that contains file and directory information. This type of vulnerability is classified under the broader category of buffer overflows and underflows, which are among the most persistent and dangerous classes of software vulnerabilities in operating systems and applications.
From an operational impact perspective, this vulnerability creates significant risk for iOS devices because it allows remote attackers to execute arbitrary code without requiring physical access or user interaction beyond the simple act of mounting the malicious disk image. The potential consequences include complete system compromise, data theft, persistent backdoor installation, and denial of service conditions that can cause device crashes or render systems unusable. Attackers can craft specially designed HFS disk images that, when processed by vulnerable iOS versions, trigger the integer underflow condition and subsequently execute malicious code within the system's privileged execution context. The vulnerability affects all iOS versions prior to 5.1, making it particularly widespread and dangerous as it impacted numerous devices that were commonly used in enterprise and consumer environments. This type of remote code execution vulnerability is especially concerning because it can be delivered through various attack vectors including email attachments, web downloads, or malicious file sharing services.
The exploitation of this vulnerability follows patterns consistent with ATT&CK technique T1059.007, which involves the use of scripting languages or system commands to execute malicious code. In this case, the attack chain begins with the delivery of a crafted HFS disk image, followed by automatic processing when the system attempts to read or mount the image, leading to the integer underflow and subsequent code execution. The vulnerability demonstrates how seemingly routine file system operations can become attack vectors when proper input validation is absent. Organizations and users were particularly vulnerable because the attack could occur automatically without user awareness, as the system would process the malicious disk image during normal file system operations. This makes the vulnerability particularly dangerous in enterprise environments where automated file processing or system integration might occur without explicit user interaction, potentially allowing attackers to gain unauthorized access to sensitive corporate data or systems.
Mitigation strategies for CVE-2012-0642 centered primarily on upgrading to iOS version 5.1 or later, which included patches addressing the integer underflow condition in HFS parsing. System administrators should have implemented comprehensive patch management procedures to ensure all iOS devices were updated promptly, as the vulnerability was actively exploited in the wild. Additional defensive measures included disabling automatic mounting of external disk images, implementing network-based filtering to prevent access to known malicious HFS disk images, and conducting regular security assessments of file system handling processes. The vulnerability highlighted the importance of robust input validation and integer overflow protection mechanisms in operating system kernels, reinforcing industry best practices for secure coding standards and the need for comprehensive security testing of file system components. Organizations should have also considered network segmentation and monitoring to detect anomalous file system access patterns that might indicate exploitation attempts, while maintaining awareness of the broader threat landscape surrounding mobile device vulnerabilities and their potential for remote code execution.