CVE-2006-3741 in Linux
Summary
by MITRE
The perfmonctl system call (sys_perfmonctl) in Linux kernel 2.4.x and 2.6 before 2.6.18, when running on Itanium systems, does not properly track the reference count for file descriptors, which allows local users to cause a denial of service (file descriptor consumption).
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Analysis
by VulDB Data Team • 04/23/2026
The vulnerability described in CVE-2006-3741 represents a critical flaw in the Linux kernel's performance monitoring subsystem specifically affecting Itanium architecture systems. This issue resides within the perfmonctl system call implementation which is responsible for managing performance monitoring events and related file descriptors. The vulnerability manifests as improper reference counting mechanisms that fail to correctly maintain file descriptor tracking during performance monitoring operations. When exploited, this flaw enables local attackers to consume excessive file descriptors leading to system resource exhaustion and potential denial of service conditions.
The technical root cause of this vulnerability stems from inadequate reference counting implementation within the kernel's performance monitoring subsystem. In the affected kernel versions 2.4.x and 2.6 before 2.6.18, the sys_perfmonctl system call fails to properly decrement reference counts when file descriptors are closed or released. This improper tracking mechanism creates a scenario where file descriptors remain allocated in memory even after they should be freed, resulting in progressive consumption of available file descriptor resources. The issue is particularly pronounced on Itanium systems due to specific architectural considerations in how performance monitoring is implemented and how file descriptor references are managed within the kernel's memory management subsystem.
From an operational impact perspective, this vulnerability presents a significant threat to system stability and availability. Local users can exploit this flaw by repeatedly invoking the perfmonctl system call with specific parameters that trigger the reference counting bug. The cumulative effect of this exploitation leads to progressive file descriptor exhaustion, ultimately causing the system to become unresponsive as it exhausts its available file descriptor limits. This type of denial of service attack can severely impact system functionality, particularly on servers or systems running performance monitoring applications where the perfmonctl functionality is regularly utilized. The vulnerability affects the fundamental resource management capabilities of the kernel, making it particularly dangerous as it operates at the kernel level where such resource exhaustion can cascade into broader system failures.
The vulnerability aligns with CWE-475, which describes improper handling of reference counts, and demonstrates characteristics consistent with the ATT&CK technique T1499.004 for network denial of service. This flaw represents a classic resource exhaustion attack vector that can be leveraged by local adversaries to degrade system performance. Organizations should implement immediate mitigation strategies including kernel version updates to 2.6.18 or later, where this vulnerability has been addressed through proper reference counting implementation. Additionally, system administrators should consider implementing monitoring for unusual file descriptor consumption patterns and limit access to performance monitoring interfaces where possible. The fix implemented in the kernel updates properly handles reference count management for file descriptors, ensuring that when performance monitoring operations complete, the associated file descriptors are correctly released and their resources returned to the system pool.