CVE-2010-0105 in Mac OS X
Summary
by MITRE
The hfs implementation in Apple Mac OS X 10.5.8 and 10.6.x before 10.6.5 supports hard links to directories and does not prevent certain deeply nested directory structures, which allows local users to cause a denial of service (filesystem corruption) via a crafted application that calls the mkdir and link functions, related to the fsck_hfs program in the diskdev_cmds component.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 01/26/2025
The vulnerability described in CVE-2010-0105 represents a critical filesystem implementation flaw within Apple Mac OS X operating systems, specifically affecting versions 10.5.8 and 10.6.x prior to 10.6.5. This issue stems from the HFS filesystem implementation which incorrectly permits the creation of hard links to directories, a functionality that should be strictly prohibited in standard filesystem designs. The flaw extends beyond simple permission violations to include inadequate protection against deeply nested directory structures that can lead to filesystem corruption. The vulnerability is particularly concerning because it affects the core filesystem functionality that underpins all file operations on Mac OS X systems, making it a fundamental security weakness that impacts system stability and integrity.
The technical exploitation of this vulnerability occurs through a carefully crafted application that leverages the mkdir and link system calls to create malformed directory structures. When the filesystem encounters these crafted directory hierarchies, the fsck_hfs program within the diskdev_cmds component fails to properly validate the directory structure, leading to filesystem corruption that manifests as denial of service conditions. This type of vulnerability falls under CWE-16, which addresses "Configuration' and specifically addresses issues related to filesystem implementation flaws and improper handling of directory structures. The vulnerability exploits the fundamental assumption that directory hard links should be impossible, as they would create circular references and potential infinite loops in directory traversal algorithms that are critical for filesystem integrity.
The operational impact of this vulnerability extends far beyond simple denial of service conditions, as filesystem corruption can result in complete system instability and data loss. Local users with minimal privileges can exploit this vulnerability to compromise the integrity of the filesystem, potentially rendering the system unusable until manual filesystem repair operations are performed. The vulnerability affects the core disk management utilities that are essential for system operation, creating a cascading effect where normal system functions become unreliable. From an attack perspective, this vulnerability aligns with ATT&CK technique T1059.001, which involves the use of command and scripting interpreters, as attackers can leverage the filesystem manipulation capabilities to create persistent conditions that degrade system performance and availability.
Mitigation strategies for this vulnerability require immediate system updates to the patched versions of Mac OS X that address the filesystem implementation flaws in the HFS subsystem. System administrators should ensure that all Mac OS X systems are updated to version 10.6.5 or later, where the filesystem validation mechanisms have been enhanced to properly prevent directory hard links and nested structure creation. Additionally, implementing monitoring for unusual filesystem operations and directory creation patterns can help detect potential exploitation attempts. The vulnerability highlights the importance of proper filesystem validation and the necessity of adhering to established filesystem design principles that prevent circular references and maintain structural integrity. Organizations should also consider implementing automated patch management systems to ensure timely deployment of security updates and prevent exploitation of similar filesystem implementation flaws that may exist in other operating system components.