CVE-2008-4219 in Mac OS X
Summary
by MITRE
The kernel in Apple Mac OS X before 10.5.6 allows local users to cause a denial of service (infinite loop and system halt) by running an application that is dynamically linked to libraries on an NFS server, related to occurrence of an exception in this application.
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Analysis
by VulDB Data Team • 08/22/2019
The vulnerability described in CVE-2008-4219 represents a critical kernel-level flaw in Apple Mac OS X versions prior to 10.5.6 that manifests through improper exception handling in the kernel's interaction with Network File System (NFS) mounted libraries. This issue occurs when a local user executes an application that is dynamically linked to shared libraries residing on an NFS server, creating a scenario where the kernel encounters an unhandled exception during the library loading process. The vulnerability falls under the category of improper exception handling within kernel space, which is classified as CWE-704 by the Common Weakness Enumeration framework, highlighting the dangerous nature of kernel-level exception management failures.
The technical exploitation of this vulnerability leverages the interaction between the Mac OS X kernel and NFS filesystem operations, specifically when the kernel attempts to resolve dynamic library dependencies from remote NFS mounts. When an application attempts to load a library from an NFS server and encounters an exceptional condition during this process, the kernel's exception handling mechanism fails to properly manage the situation, resulting in an infinite loop that consumes system resources and ultimately causes the entire system to halt. This behavior constitutes a classic denial of service attack that can be executed by any local user with the ability to run applications, making it particularly concerning for multi-user environments where system stability is paramount.
The operational impact of CVE-2008-4219 extends beyond simple system unavailability, as it represents a fundamental failure in the kernel's ability to maintain system integrity when encountering remote filesystem exceptions. Attackers can reliably trigger this condition by crafting applications that dynamically link to libraries on NFS shares, making the vulnerability particularly dangerous in enterprise environments where NFS is commonly used for shared storage solutions. The infinite loop behavior demonstrates a lack of proper timeout mechanisms and exception recovery procedures within the kernel's NFS subsystem, which is consistent with ATT&CK framework technique T1499.004 for denial of service through resource exhaustion. This vulnerability effectively allows any local user to compromise system availability without requiring elevated privileges, creating a significant risk for systems where unauthorized users might have access to run arbitrary applications.
Mitigation strategies for this vulnerability involve immediate system updates to Mac OS X 10.5.6 or later versions where Apple has implemented proper exception handling for NFS library loading scenarios. Organizations should also consider restricting local users' ability to execute applications that might dynamically link to remote NFS resources, implementing proper access controls and monitoring for suspicious library loading patterns. The vulnerability highlights the importance of robust kernel exception handling and proper resource management in preventing denial of service conditions that can be triggered through seemingly benign user activities. System administrators should implement monitoring solutions to detect unusual patterns of NFS access that might indicate exploitation attempts, while also ensuring that NFS mounts are properly configured with appropriate security settings to limit potential attack vectors.