CVE-2009-3527 in FreeBSD
Summary
by MITRE
Race condition in the Pipe (IPC) close function in FreeBSD 6.3 and 6.4 allows local users to cause a denial of service (crash) or gain privileges via vectors related to kqueues, which triggers a use after free, leading to a NULL pointer dereference or memory corruption.
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Analysis
by VulDB Data Team • 09/15/2024
The vulnerability identified as CVE-2009-3527 represents a critical race condition within the inter-process communication mechanisms of FreeBSD operating systems version 6.3 and 6.4. This flaw specifically manifests in the Pipe close function where improper synchronization allows malicious local users to exploit temporal gaps in the system's resource management. The vulnerability leverages the kqueue subsystem which serves as a scalable event notification interface for monitoring file descriptors and other system resources. When a pipe is closed while concurrent operations are occurring, the timing window creates opportunities for attackers to manipulate the system's internal data structures.
The technical exploitation of this vulnerability occurs through a use-after-free condition that arises when the pipe close operation attempts to access memory that has already been deallocated. This particular race condition allows attackers to manipulate the kernel's memory management by carefully orchestrating the timing of pipe operations and kqueue events. The flaw results in a NULL pointer dereference or more severe memory corruption that can lead to system crashes or potentially privilege escalation. The underlying issue stems from insufficient locking mechanisms during the pipe cleanup process, where multiple threads or processes can simultaneously access and modify the same kernel data structures without proper mutual exclusion.
From an operational impact perspective, this vulnerability presents significant risks to FreeBSD systems running the affected versions as local users can either cause system instability through denial of service attacks or potentially escalate privileges to gain elevated system access. The race condition's nature makes it particularly challenging to detect and exploit reliably, though successful exploitation can result in complete system compromise. The vulnerability affects systems where multiple processes interact through pipes and kqueues, which is common in server environments and applications requiring complex inter-process communication. Security implications extend beyond simple crashes as the memory corruption could potentially be leveraged for more sophisticated attacks targeting kernel memory layout or privilege escalation.
Mitigation strategies for CVE-2009-3527 should prioritize immediate system updates to patched FreeBSD versions that address the synchronization issues in the pipe close function. System administrators should implement monitoring for unusual pipe and kqueue operations that might indicate exploitation attempts. The vulnerability aligns with CWE-362, which classifies race conditions in concurrent programming, and relates to ATT&CK technique T1068, involving privilege escalation through kernel exploits. Additional defensive measures include restricting local user access where possible, implementing proper process isolation, and maintaining comprehensive system logging to detect anomalous pipe and kqueue behavior. Organizations should also consider applying kernel hardening patches and ensuring all systems are updated to supported FreeBSD releases that contain the necessary synchronization fixes for the pipe subsystem.