CVE-2021-30919 in macOS
Summary
by MITRE • 08/25/2021
An out-of-bounds write was addressed with improved input validation. This issue is fixed in iOS 15.1 and iPadOS 15.1, macOS Monterey 12.0.1, iOS 14.8.1 and iPadOS 14.8.1, tvOS 15.1, watchOS 8.1, Security Update 2021-007 Catalina, macOS Big Sur 11.6.1. Processing a maliciously crafted PDF may lead to arbitrary code execution.
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Analysis
by VulDB Data Team • 10/31/2021
This vulnerability represents a critical out-of-bounds write flaw that exists within Apple's PDF processing libraries across multiple operating systems. The issue stems from insufficient input validation when handling maliciously crafted PDF files, allowing attackers to manipulate memory locations beyond the intended boundaries. The vulnerability affects a wide range of Apple products including iOS, iPadOS, macOS, tvOS, and watchOS versions prior to the specified security updates. From a cybersecurity perspective, this represents a significant risk as PDF files are ubiquitous in enterprise and personal environments, making exploitation vectors abundant and potentially devastating.
The technical nature of this vulnerability places it squarely within the CWE-787 category of out-of-bounds write conditions, where an attacker can write data beyond the allocated memory buffer. This type of flaw typically occurs when applications fail to properly validate input data lengths or boundaries before processing. The exploitation mechanism relies on carefully crafted PDF documents that trigger memory corruption during parsing operations, potentially allowing attackers to execute arbitrary code with the privileges of the affected application. This aligns with ATT&CK technique T1203, which describes the use of malicious documents to gain initial access or execute code through application vulnerabilities.
The operational impact of this vulnerability extends beyond simple code execution, as it provides attackers with potential persistence mechanisms and privilege escalation opportunities. When exploited successfully, this vulnerability could allow threat actors to compromise user devices, access sensitive data, or establish footholds within network environments. The widespread adoption of Apple's ecosystem means that a single exploited vulnerability could affect millions of devices across multiple platforms simultaneously. Security teams must consider the implications of this vulnerability when assessing risk in environments where Apple devices are prevalent, particularly in sectors handling sensitive information.
Mitigation strategies should prioritize immediate deployment of the vendor-provided security updates across all affected systems. Organizations should implement network monitoring to detect potential exploitation attempts through PDF file transfers and consider deploying sandboxing solutions for PDF processing. The remediation process requires coordinated updates across multiple operating system versions, with particular attention to macOS Catalina and Big Sur users who require specific security update packages. Security controls should also include user education about avoiding suspicious PDF files and implementing strict file validation policies for document handling within enterprise environments. The vulnerability underscores the importance of maintaining up-to-date security patches and demonstrates how seemingly benign file processing functions can represent significant attack surface areas.