CVE-2021-30879 in macOS
Summary
by MITRE • 08/25/2021
An out-of-bounds read was addressed with improved bounds checking. This issue is fixed in macOS Monterey 12.0.1, Security Update 2021-007 Catalina, macOS Big Sur 11.6.1. Processing a maliciously crafted AppleScript binary may result in unexpected application termination or disclosure of process memory.
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Analysis
by VulDB Data Team • 10/31/2021
The vulnerability identified as CVE-2021-30879 represents a critical out-of-bounds read flaw within Apple's operating system ecosystem, specifically affecting macOS versions prior to the aforementioned security updates. This type of vulnerability falls under the common weakness enumeration CWE-125, which classifies out-of-bounds read conditions that can lead to unpredictable behavior and potential information disclosure. The flaw manifests when the system processes maliciously crafted AppleScript binary files, creating a scenario where legitimate applications may encounter unexpected termination or expose sensitive process memory contents to unauthorized parties.
The technical implementation of this vulnerability stems from inadequate bounds checking mechanisms within the AppleScript processing subsystem. When an application encounters a crafted AppleScript binary, the parsing routine fails to properly validate array or buffer boundaries before accessing memory locations. This oversight allows an attacker to manipulate the input data in such a way that the application attempts to read memory beyond its allocated boundaries. The root cause aligns with ATT&CK technique T1059.007 for AppleScript, where adversaries leverage scripting languages to execute malicious code or exploit weaknesses in script processing engines.
The operational impact of this vulnerability extends beyond simple application crashes, presenting significant security implications for macOS environments. Uncontrolled application termination can disrupt user workflows and potentially provide attackers with information about system state or memory layout, which could facilitate further exploitation attempts. Memory disclosure represents a particularly concerning aspect as it may reveal sensitive data such as cryptographic keys, user credentials, or internal application structures that could be leveraged for privilege escalation or lateral movement within a compromised system.
Organizations and users must prioritize immediate deployment of the available security patches to mitigate this vulnerability. The recommended updates include macOS Monterey 12.0.1, Security Update 2021-007 for Catalina, and macOS Big Sur 11.6.1, which contain the necessary bounds checking improvements. System administrators should implement comprehensive patch management procedures to ensure all endpoints receive these critical updates. Additionally, organizations should consider implementing monitoring solutions to detect potential exploitation attempts through anomalous AppleScript processing activities. The vulnerability serves as a reminder of the importance of robust input validation and memory safety practices in system-level software development, particularly when handling user-supplied data through interpreted scripting languages.