CVE-2021-1741 in tvOS
Summary
by MITRE • 04/03/2021
An out-of-bounds read was addressed with improved bounds checking. This issue is fixed in macOS Big Sur 11.2, Security Update 2021-001 Catalina, Security Update 2021-001 Mojave, watchOS 7.3, tvOS 14.4, iOS 14.4 and iPadOS 14.4. Processing a maliciously crafted image may lead to arbitrary code execution.
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Analysis
by VulDB Data Team • 04/08/2021
This vulnerability represents a critical out-of-bounds read flaw that affects multiple Apple operating systems including macOS Big Sur, iOS, watchOS, and tvOS. The issue stems from insufficient bounds checking during image processing operations, where the affected systems fail to properly validate array indices or memory boundaries when handling specially crafted image files. Such vulnerabilities typically arise when software does not adequately verify input parameters before accessing memory locations, creating opportunities for attackers to manipulate program execution flow. The flaw specifically manifests when processing maliciously crafted images that contain malformed data structures designed to trigger buffer over-read conditions.
The technical implementation of this vulnerability involves the image parsing subsystem where memory access occurs beyond allocated buffer boundaries. When an attacker crafts an image file with malicious metadata or pixel data, the parsing routine fails to validate the bounds of array accesses, potentially allowing adjacent memory regions to be read. This type of flaw falls under the CWE-129 vulnerability category, which specifically addresses insufficient bounds checking in array access operations. The vulnerability can be leveraged for arbitrary code execution through a technique known as information disclosure followed by code execution, where the out-of-bounds read provides attackers with sensitive memory contents that can be used to bypass security mitigations or craft further exploits.
The operational impact of this vulnerability extends across multiple device types and operating system versions, making it particularly concerning for enterprise and individual users alike. Attackers could potentially deliver malicious image files through various vectors including email attachments, web downloads, or malicious applications that process image content. The exploit chain typically begins with the delivery of a crafted image file that triggers the vulnerable code path during image rendering or processing operations. Once triggered, the out-of-bounds read could allow attackers to access memory locations containing sensitive data, potentially leading to privilege escalation or full system compromise. This vulnerability aligns with ATT&CK technique T1059.007 for command and scripting interpreter, as successful exploitation could enable attackers to execute arbitrary commands on affected systems.
Apple addressed this vulnerability through comprehensive bounds checking improvements in their image processing libraries across all supported operating system versions. The security updates include enhanced validation routines that properly check array indices before memory access operations, preventing unauthorized memory reads. Organizations should prioritize deployment of these security updates across all affected systems, particularly those handling untrusted image content. The mitigation strategy involves not only applying the official patches but also implementing additional security controls such as image sanitization for incoming content, network-based filtering for suspicious image files, and regular security assessments to identify potential exploitation attempts. System administrators should monitor for any indicators of compromise related to image processing activities and maintain updated threat intelligence feeds to detect potential exploitation attempts targeting this specific vulnerability.