CVE-2015-6984 in Mac OS X
Summary
by MITRE
libarchive in Apple OS X before 10.11.1 allows attackers to write to arbitrary files via a crafted app that conducts an unspecified symlink attack.
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Analysis
by VulDB Data Team • 11/21/2024
The vulnerability identified as CVE-2015-6984 affects libarchive, a widely used library for handling various archive formats within Apple's operating systems. This flaw exists in versions of macOS prior to 10.11.1 and represents a significant security weakness that could be exploited by malicious actors to gain unauthorized file system access. The vulnerability specifically manifests when processing crafted applications that leverage symlink attacks, creating a pathway for arbitrary file writing operations. This type of vulnerability falls under the category of insecure file handling and improper access control mechanisms, where the system fails to properly validate or sanitize file paths during archive extraction processes.
The technical implementation of this vulnerability stems from how libarchive processes symbolic links within archive files. When an attacker crafts a malicious application containing specially constructed symbolic links, the library may follow these links and write data to unintended locations on the file system. This occurs because the archive extraction process does not adequately verify the target destinations of symbolic links, allowing attackers to redirect file operations to sensitive system locations or other unauthorized directories. The flaw essentially bypasses normal file system access controls and validation mechanisms that should prevent arbitrary file writing operations. This vulnerability is categorized as a symlink attack, which is commonly classified under CWE-59 as "Improper Link Resolution" and aligns with ATT&CK technique T1059.007 for "Command and Scripting Interpreter: PowerShell" when considering the broader exploitation patterns.
The operational impact of CVE-2015-6984 extends beyond simple file system manipulation, as it can enable attackers to escalate privileges and potentially compromise entire systems. An attacker could leverage this vulnerability to overwrite critical system files, install malicious software, or modify configuration settings that affect system behavior and security posture. The vulnerability is particularly dangerous because it can be exploited through seemingly benign applications that users might legitimately download or execute, making it difficult to detect and prevent. This type of attack can be particularly effective in social engineering campaigns where users are tricked into executing malicious applications that contain the crafted archive files. The vulnerability also represents a significant risk to enterprise environments where automated deployment processes or user applications might inadvertently trigger the exploit.
Mitigation strategies for CVE-2015-6984 primarily focus on updating to affected systems to macOS 10.11.1 or later versions where Apple has implemented patches addressing the symlink handling behavior in libarchive. Organizations should also implement strict application whitelisting policies that prevent execution of untrusted applications, particularly those that might contain archive files with suspicious symbolic link structures. Network-level protections including firewalls and intrusion detection systems can help monitor for suspicious file extraction activities. Additionally, system administrators should conduct regular security audits to identify and remove potentially malicious applications that might exploit this vulnerability. The fix implemented by Apple addresses the core issue by enhancing the validation of symbolic links during archive processing and ensuring that file system operations respect proper access controls. Security teams should also consider implementing monitoring solutions that track file system modifications and can alert on unusual patterns that might indicate exploitation attempts. This vulnerability highlights the importance of proper input validation and the need for robust security controls in library and framework implementations that handle file system operations.