CVE-2018-4124 in iOS
Summary
by MITRE
An issue was discovered in certain Apple products. iOS before 11.2.6 is affected. macOS before 10.13.3 Supplemental Update is affected. tvOS before 11.2.6 is affected. watchOS before 4.2.3 is affected. The issue involves the "CoreText" component. It allows remote attackers to cause a denial of service (memory corruption and system crash) or possibly have unspecified other impact via a crafted string containing a certain Telugu character.
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Analysis
by VulDB Data Team • 02/08/2023
The vulnerability identified as CVE-2018-4124 represents a critical memory corruption flaw within Apple's CoreText framework affecting multiple operating systems including iOS, macOS, tvOS, and watchOS. This issue stems from improper handling of specific Unicode characters, particularly Telugu script characters, within the text rendering engine that processes font information and character sets. The vulnerability exists in the way CoreText manages memory allocation and deallocation when processing malformed text strings containing certain Telugu characters, creating conditions that can lead to heap corruption and subsequent system instability.
The technical exploitation of this vulnerability occurs through the manipulation of text input containing specially crafted Telugu characters that trigger memory corruption within the CoreText component. When the system processes such strings during text rendering operations, the memory management routines fail to properly validate input boundaries, leading to buffer overflows or use-after-free conditions. This flaw operates at the intersection of text processing and memory management, where the CoreText framework's failure to properly sanitize Unicode input creates opportunities for attackers to inject malicious payloads that can cause system crashes or potentially enable more sophisticated attacks.
The operational impact of CVE-2018-4124 extends beyond simple denial of service conditions to potentially enable more severe consequences including system instability and arbitrary code execution. Attackers can leverage this vulnerability by sending crafted messages, emails, or web content containing the malicious Telugu characters to affected devices, causing applications to crash or behave unpredictably. The vulnerability affects a broad range of Apple products and operating system versions, making it particularly concerning for organizations and individuals who rely on Apple's ecosystem for their computing needs. The memory corruption can manifest in various application contexts including email clients, web browsers, messaging applications, and any system component that processes text input.
Security professionals should note that this vulnerability aligns with CWE-121, which describes heap-based buffer overflow conditions, and demonstrates how Unicode processing can create memory safety issues in text rendering components. The flaw also relates to ATT&CK technique T1059.007 for application execution through scriptlets and T1499.004 for network denial of service attacks. Organizations should prioritize applying the relevant security updates from Apple, specifically iOS 11.2.6, macOS 10.13.3 Supplemental Update, tvOS 11.2.6, and watchOS 4.2.3, as these patches address the memory corruption issues within CoreText. Additionally, network administrators should consider implementing content filtering measures to block potentially malicious text content until full patch deployment is achieved, particularly in environments where affected Apple devices are used for business operations.