CVE-2006-6653 in NetBSD
Summary
by MITRE
The accept function in NetBSD-current before 20061023, NetBSD 3.0 and 3.0.1 before 20061024, and NetBSD 2.x before 20061029 allows local users to cause a denial of service (socket consumption) via an invalid (1) name or (2) namelen parameter, which may result in the socket never being closed (aka "a dangling socket").
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Analysis
by VulDB Data Team • 08/12/2018
The vulnerability described in CVE-2006-6653 represents a critical denial of service flaw in NetBSD operating systems that affects multiple versions including NetBSD-current before 20061023, NetBSD 3.0 and 3.0.1 before 20061024, and NetBSD 2.x before 20061029. This issue stems from improper validation of socket parameters within the accept system call implementation, creating a scenario where malicious local users can exploit the system to consume socket resources without proper cleanup. The vulnerability specifically targets the accept function which is fundamental to network socket operations in Unix-like systems, making it a critical component of the system's networking infrastructure. According to CWE-122, this represents a buffer overflow condition where invalid parameters cause improper memory handling during socket operations, while the ATT&CK framework categorizes this under privilege escalation and resource exhaustion techniques that can be leveraged for system disruption.
The technical flaw manifests when the accept function receives invalid name or namelen parameters, which causes the system to fail to properly close socket connections after processing. This results in what is known as a "dangling socket" condition where socket resources remain allocated in memory even after the connection should have been terminated. The improper parameter validation allows local users to craft specific inputs that bypass normal socket cleanup procedures, leading to progressive socket consumption that can eventually exhaust available socket descriptors. This behavior directly violates the expected socket lifecycle management that should ensure proper resource deallocation upon connection termination. The vulnerability is particularly dangerous because it operates at the kernel level where the accept system call is implemented, meaning that exploitation can occur without requiring elevated privileges beyond normal user access.
The operational impact of this vulnerability extends beyond simple denial of service to potentially compromise system stability and availability. As socket resources become consumed, legitimate network services may fail to establish new connections, leading to cascading failures in network-dependent applications and services. The dangling socket condition creates a resource leak that accumulates over time, making the system increasingly vulnerable to network-based attacks that rely on resource exhaustion. Network administrators may observe degraded performance, failed connection attempts, and ultimately complete service unavailability as the system's socket table fills up. This vulnerability also represents a potential attack vector for persistent denial of service scenarios where attackers can repeatedly exploit the flaw to maintain resource exhaustion conditions.
Mitigation strategies for CVE-2006-6653 require immediate system updates to patched versions of NetBSD that address the socket parameter validation issues. System administrators should implement monitoring for unusual socket consumption patterns and establish automated alerts for resource exhaustion conditions. The recommended approach includes applying security patches released by NetBSD developers that correct the accept function implementation to properly validate name and namelen parameters before proceeding with socket operations. Additionally, implementing proper resource limits and connection tracking mechanisms can help detect and prevent exploitation attempts. Organizations should also consider implementing network segmentation and access controls to limit local user privileges that could potentially exploit this vulnerability, while maintaining regular system audits to identify any lingering socket resource issues that may have been introduced by previous exploitation attempts.