CVE-2001-1047 in OpenBSD
Summary
by MITRE
Race condition in OpenBSD VFS allows local users to cause a denial of service (kernel panic) by (1) creating a pipe in one thread and causing another thread to set one of the file descriptors to NULL via a close, or (2) calling dup2 on a file descriptor in one process, then setting the descriptor to NULL via a close in another process that is created via rfork.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 07/04/2014
The vulnerability described in CVE-2001-1047 represents a critical race condition within the OpenBSD Virtual File System (VFS) implementation that exposes the operating system to potential denial of service attacks. This flaw manifests when multiple threads or processes attempt to manipulate file descriptors simultaneously, creating a scenario where the kernel's internal state becomes inconsistent and ultimately leads to a kernel panic. The race condition specifically affects the handling of pipe file descriptors and their associated file descriptor management, making it particularly dangerous in multi-threaded environments where concurrent access to shared resources is common.
The technical implementation of this vulnerability exploits the timing dependencies between concurrent operations within the kernel's file descriptor management subsystem. When a pipe is created in one thread while another thread simultaneously attempts to close and nullify the file descriptor reference, the kernel fails to properly synchronize these operations. This synchronization failure occurs at the VFS layer where the kernel maintains references to file descriptor structures and their associated pipe endpoints. The flaw also extends to processes created via rfork operations, where the dup2 system call combined with concurrent close operations creates similar race conditions that can corrupt kernel memory structures and lead to system crashes.
The operational impact of CVE-2001-1047 extends beyond simple denial of service, as it can potentially compromise system stability and availability in production environments. Local attackers who understand the timing requirements of the race condition can reliably trigger kernel panics, forcing system administrators to reboot affected systems and potentially disrupting critical services. This vulnerability particularly affects systems where multiple threads or processes frequently create and manipulate pipes for inter-process communication, making it a significant concern for servers and applications that rely heavily on concurrent file descriptor operations. The vulnerability demonstrates poor adherence to concurrency control principles and highlights the importance of proper kernel-level synchronization mechanisms.
The root cause of this vulnerability aligns with CWE-362, which describes a race condition in the context of concurrent execution and resource management. This weakness specifically manifests in the kernel's handling of file descriptor references during pipe operations, where insufficient locking mechanisms allow multiple threads to access and modify the same kernel data structures simultaneously. From an ATT&CK framework perspective, this vulnerability maps to techniques involving privilege escalation and system stability compromise, as local users can leverage this flaw to cause system-wide disruptions. The vulnerability also relates to CWE-116, which addresses improper handling of synchronization primitives, further emphasizing the need for proper kernel-level thread synchronization and resource management. Mitigation strategies should focus on implementing proper locking mechanisms around critical sections of code that handle pipe file descriptor operations, ensuring that all concurrent access to kernel data structures is properly synchronized. System administrators should consider applying kernel patches that address the specific race condition in the VFS layer, while developers should review concurrent code patterns to ensure proper use of atomic operations and synchronization primitives when working with kernel-level file descriptor management.