CVE-2021-30833 in macOS
Summary
by MITRE • 10/28/2021
This issue was addressed with improved checks. This issue is fixed in macOS Monterey 12.0.1. Unpacking a maliciously crafted archive may allow an attacker to write arbitrary files.
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Analysis
by VulDB Data Team • 10/31/2021
The vulnerability described in CVE-2021-30833 represents a critical file extraction flaw affecting macOS systems prior to version 12.0.1. This issue specifically targets the archive unpacking functionality within the operating system, creating a path for malicious actors to exploit the underlying file handling mechanisms. The vulnerability stems from insufficient validation during the decompression process, allowing attackers to craft specially designed archive files that can bypass normal file system security controls. This type of vulnerability falls under the category of archive extraction attacks and can be classified as a CWE-400 vulnerability related to uncontrolled resource consumption or more specifically CWE-770 for allocation of resources without limits or throttling.
The technical exploitation of this vulnerability occurs when a user or automated process extracts a maliciously crafted archive file. During the unpacking operation, the system fails to properly validate file paths or directory structures contained within the archive, enabling attackers to manipulate the extraction process to write files to arbitrary locations on the filesystem. This behavior aligns with ATT&CK technique T1059.007 for command and scripting interpreter and potentially T1566 for phishing with social engineering. The flaw essentially allows for a form of path traversal or directory traversal attack where the attacker can specify absolute paths or manipulate relative paths to place malicious files in sensitive system directories or user locations.
The operational impact of CVE-2021-30833 extends beyond simple file overwriting capabilities, as it can enable privilege escalation scenarios when combined with other attack vectors. An attacker who successfully exploits this vulnerability could potentially place malicious executables in system directories, modify configuration files, or create persistence mechanisms that would execute with elevated privileges. The vulnerability is particularly dangerous in enterprise environments where users may unknowingly extract compromised archive files from untrusted sources, including email attachments, download packages, or web-based file transfers. This issue affects not only individual users but also organizations that rely on macOS systems for business operations and may have automated processes that handle file extraction.
Mitigation strategies for this vulnerability primarily focus on immediate system updates and operational security improvements. The most effective solution is to upgrade to macOS Monterey version 12.0.1 or later, which includes the necessary patches that address the flawed archive unpacking logic. Organizations should implement comprehensive patch management procedures to ensure all macOS systems are updated promptly, as this vulnerability could be exploited in targeted attacks against specific user groups. Additional protective measures include implementing strict file validation policies for archive files, particularly those received from external sources, and educating users about the risks of extracting unknown or untrusted archive files. Network-based controls such as email filtering and web proxy configurations can help prevent the delivery of malicious archive files to end users. Security monitoring should include detection of unusual file creation patterns in system directories, as this vulnerability could be used to establish persistent backdoors or deploy additional malware components. The remediation process should also consider implementing sandboxing mechanisms for archive processing and ensuring that file extraction operations occur in restricted environments with minimal privileges.