CVE-2007-6599 in OpenAFS
Summary
by MITRE
Race condition in fileserver in OpenAFS 1.3.50 through 1.4.5 and 1.5.0 through 1.5.27 allows remote attackers to cause a denial of service (daemon crash) by simultaneously acquiring and giving back file callbacks, which causes the handler for the GiveUpAllCallBacks RPC to perform linked-list operations without the host_glock lock.
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Analysis
by VulDB Data Team • 08/03/2019
The vulnerability identified as CVE-2007-6599 represents a critical race condition within the fileserver component of OpenAFS versions 1.3.50 through 1.4.5 and 1.5.0 through 1.5.27. This flaw specifically targets the synchronization mechanisms employed by the distributed file system, creating a scenario where concurrent operations can lead to system instability and service disruption. The vulnerability stems from improper handling of linked-list operations within the GiveUpAllCallBacks RPC handler, which is a fundamental component responsible for managing file callback operations in the OpenAFS architecture.
The technical implementation of this race condition occurs when remote attackers exploit the lack of proper locking mechanisms during simultaneous acquisition and release of file callbacks. The fileserver daemon operates under a multi-threaded environment where multiple clients can request callback operations concurrently, but the GiveUpAllCallBacks RPC handler fails to acquire the necessary host_glock lock before performing linked-list modifications. This omission creates a window where concurrent threads can access and modify the same data structures without proper synchronization, leading to memory corruption and eventual daemon crashes. The vulnerability operates at the core of OpenAFS's callback management system, which is essential for maintaining cache consistency across distributed nodes in the file system.
The operational impact of this vulnerability extends beyond simple denial of service to potentially compromise the integrity of the distributed file system. When the daemon crashes due to the race condition, it disrupts file access for all clients connected to the affected OpenAFS server, causing widespread service interruption. The vulnerability's remote exploitability means that attackers do not require local system access to trigger the condition, making it particularly dangerous in networked environments where OpenAFS servers are exposed to external networks. This flaw can be leveraged by attackers to perform persistent denial of service attacks against critical file services, potentially affecting business continuity and data availability for organizations relying on OpenAFS for distributed storage management.
Mitigation strategies for this vulnerability require immediate patching of affected OpenAFS versions to address the synchronization issues in the callback handling code. System administrators should prioritize upgrading to patched versions of OpenAFS where proper locking mechanisms have been implemented for the GiveUpAllCallBacks RPC handler. Additionally, network segmentation and access controls should be implemented to limit exposure of OpenAFS servers to untrusted networks, reducing the attack surface for remote exploitation attempts. The vulnerability aligns with CWE-362, which describes race conditions in software systems, and represents a classic example of improper locking in concurrent programming that violates fundamental security principles outlined in the ATT&CK framework under privilege escalation and denial of service techniques. Organizations should also implement monitoring solutions to detect anomalous callback behavior and potential exploitation attempts, while maintaining regular security assessments of their distributed file system infrastructure to identify similar synchronization vulnerabilities.