CVE-2009-3547 in Linux
Summary
by MITRE
Multiple race conditions in fs/pipe.c in the Linux kernel before 2.6.32-rc6 allow local users to cause a denial of service (NULL pointer dereference and system crash) or gain privileges by attempting to open an anonymous pipe via a /proc/*/fd/ pathname.
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Analysis
by VulDB Data Team • 12/19/2024
The vulnerability described in CVE-2009-3547 represents a critical race condition flaw within the Linux kernel's pipe implementation, specifically in the fs/pipe.c file. This issue affects kernel versions prior to 2.6.32-rc6 and demonstrates how improper synchronization mechanisms can lead to severe system instability. The vulnerability exploits a timing window where concurrent access to pipe operations creates inconsistent states that can be manipulated by local attackers. The race condition occurs during the process of opening anonymous pipes through /proc/*/fd/ pathnames, which provides a unique attack vector that leverages the kernel's file descriptor handling mechanisms.
The technical implementation of this vulnerability stems from insufficient locking mechanisms in the pipe subsystem when handling concurrent access to pipe file descriptors. When a local user attempts to open an anonymous pipe through the /proc/*/fd/ interface, the kernel's pipe allocation and reference counting mechanisms fail to properly synchronize access between multiple concurrent processes or threads. This creates a window where the pipe structure can be freed while still being accessed, leading to NULL pointer dereferences that ultimately cause system crashes or kernel oops messages. The flaw is particularly dangerous because it can be exploited to achieve privilege escalation, allowing attackers to gain elevated system privileges through carefully crafted race condition scenarios.
From an operational impact perspective, this vulnerability presents a significant threat to system stability and security integrity. Local users can exploit the race condition to either cause system crashes through NULL pointer dereferences or to escalate privileges by manipulating the timing of pipe operations. The denial of service aspect can be used to disrupt services or cause system instability, while the privilege escalation component allows attackers to gain root access to compromised systems. The vulnerability is particularly concerning because it requires minimal privileges to exploit and can be triggered through standard user-level operations, making it an attractive target for both casual attackers and more sophisticated threat actors. The attack can be executed without requiring special permissions or hardware access, simply through normal user processes attempting to access pipe file descriptors.
Mitigation strategies for CVE-2009-3547 focus primarily on kernel updates and system hardening measures. The most effective solution is to upgrade to Linux kernel versions 2.6.32-rc6 or later, where the race conditions have been properly addressed through improved locking mechanisms and synchronization primitives. System administrators should implement regular kernel updates and maintain current security patches to protect against similar vulnerabilities. Additional protective measures include monitoring for unusual pipe operations and implementing process isolation techniques to limit potential attack surfaces. The vulnerability aligns with CWE-362, which describes race conditions in concurrent programming, and maps to ATT&CK technique T1068, which covers local privilege escalation through kernel vulnerabilities. Organizations should also consider implementing kernel lockdown mechanisms and restricting access to /proc filesystem interfaces to minimize exploitation opportunities. The incident highlights the critical importance of proper synchronization in kernel-level code and demonstrates how seemingly minor concurrency issues can result in severe security implications.