CVE-2011-1083 in Linux
Summary
by MITRE
The epoll implementation in the Linux kernel 2.6.37.2 and earlier does not properly traverse a tree of epoll file descriptors, which allows local users to cause a denial of service (CPU consumption) via a crafted application that makes epoll_create and epoll_ctl system calls.
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Analysis
by VulDB Data Team • 08/18/2024
The vulnerability identified as CVE-2011-1083 resides within the Linux kernel's epoll implementation, specifically affecting versions through 2.6.37.2. This flaw represents a critical design oversight in how the kernel manages epoll file descriptor trees, creating a potential avenue for denial of service attacks that can consume excessive CPU resources. The epoll mechanism serves as a scalable event notification interface that allows applications to monitor multiple file descriptors simultaneously, making it a fundamental component of high-performance networking applications and system services. When exploited, this vulnerability demonstrates the dangerous consequences of improper tree traversal algorithms in kernel space, where a single flawed implementation can compromise system stability and availability.
The technical flaw manifests in the improper traversal of a data structure that organizes epoll file descriptors within the kernel's memory management system. This tree-based organization is designed to efficiently manage multiple file descriptors and their associated events, but the implementation contains a critical bug in its traversal logic. When applications utilize epoll_create and epoll_ctl system calls in specific patterns, the kernel's epoll subsystem enters an infinite loop or extremely inefficient traversal path that consumes CPU cycles without proper bounds. The vulnerability is particularly insidious because it requires minimal privileges and can be triggered by any local user, making it an attractive vector for attackers seeking to disrupt system operations without requiring elevated access rights. This flaw directly corresponds to CWE-121, which addresses buffer overflow conditions, and more specifically relates to improper handling of data structures in kernel space.
The operational impact of CVE-2011-1083 extends beyond simple resource exhaustion, as it can lead to complete system unresponsiveness and denial of service across all services relying on epoll functionality. Local users can craft malicious applications that exploit this vulnerability to consume 100% CPU utilization, effectively rendering the system unusable for legitimate operations. Network services, web servers, database systems, and other applications that depend on epoll for efficient I/O handling become vulnerable to this attack vector. The attack requires no special privileges beyond standard user access, making it particularly dangerous in multi-tenant environments where users might have legitimate access to system resources. This vulnerability also aligns with ATT&CK technique T1499.001, which covers network denial of service attacks, and represents a classic example of how kernel-level flaws can create systemic security issues that affect entire computing environments.
Mitigation strategies for CVE-2011-1083 primarily focus on upgrading to kernel versions that contain the necessary patches, with Linux kernel 2.6.38 and later versions providing the required fixes. System administrators should prioritize patching affected systems, as the vulnerability does not require any special privileges for exploitation and can be triggered by any local user. Additionally, monitoring for unusual CPU consumption patterns and implementing proper system hardening measures can help detect exploitation attempts. The fix implemented in patched versions addresses the root cause by correcting the tree traversal algorithm to prevent infinite loops and ensure proper bounds checking. Organizations should also consider implementing application-level restrictions and monitoring to prevent unauthorized applications from creating potentially malicious epoll configurations, though the most effective mitigation remains the timely application of kernel security updates.