CVE-2011-2189 in Linux
Summary
by MITRE
net/core/net_namespace.c in the Linux kernel 2.6.32 and earlier does not properly handle a high rate of creation and cleanup of network namespaces, which makes it easier for remote attackers to cause a denial of service (memory consumption) via requests to a daemon that requires a separate namespace per connection, as demonstrated by vsftpd.
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Analysis
by VulDB Data Team • 01/12/2025
The vulnerability described in CVE-2011-2189 represents a significant denial of service weakness within the Linux kernel's network namespace management system. This flaw exists in the net/core/net_namespace.c file of kernel versions 2.6.32 and earlier, where the implementation fails to adequately manage the rapid creation and destruction of network namespaces. The issue becomes particularly problematic when applications must establish separate network namespaces for each connection, creating a scenario where the kernel's namespace management subsystem cannot efficiently handle the high-frequency operations required by such daemons.
The technical implementation flaw stems from inadequate synchronization and resource cleanup mechanisms within the kernel's namespace handling code. When network namespaces are created and destroyed at a rapid pace, the kernel's memory management system experiences inefficient resource utilization patterns that can lead to progressive memory consumption. This occurs because the cleanup process for network namespaces does not properly account for the high-frequency nature of their creation and destruction cycles, resulting in memory fragmentation and accumulation of unreleased resources over time. The vulnerability specifically impacts systems where network daemon applications require per-connection namespace isolation, making the attack vector particularly relevant for services like vsftpd that establish separate network namespaces for each client connection.
The operational impact of this vulnerability extends beyond simple resource exhaustion, creating potential system instability and service disruption for legitimate users. Remote attackers can exploit this weakness by repeatedly initiating connection requests to vulnerable daemons, causing the target system to consume increasing amounts of memory until system performance degrades significantly or complete denial of service occurs. The attack demonstrates how poorly managed kernel resources can be leveraged to create cascading failures in network services, particularly affecting server applications that rely heavily on namespace isolation for security boundaries. This vulnerability essentially provides an attacker with a straightforward method to consume system resources without requiring elevated privileges or complex exploitation techniques.
The mitigation strategies for CVE-2011-2189 involve both immediate system updates and operational adjustments to reduce the attack surface. Kernel version upgrades to 2.6.33 or later are essential since this vulnerability was addressed in subsequent releases through improved namespace management and memory cleanup mechanisms. System administrators should also consider implementing connection rate limiting and resource monitoring for network services that create network namespaces, particularly those that are exposed to untrusted networks. Additionally, the vulnerability aligns with attack patterns documented in the MITRE ATT&CK framework under the denial of service category, specifically targeting resource exhaustion techniques that can be applied to kernel-level components. This issue is classified under CWE-400, which addresses improper resource management in software systems, highlighting the fundamental problem of inadequate memory lifecycle management within kernel space operations. Organizations should implement comprehensive monitoring solutions to detect unusual memory consumption patterns that may indicate exploitation attempts against this vulnerability.