CVE-2001-0830 in 6tunnel
Summary
by MITRE
6tunnel 0.08 and earlier does not properly close sockets that were initiated by a client, which allows remote attackers to cause a denial of service (resource exhaustion) by repeatedly connecting to and disconnecting from the server.
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Analysis
by VulDB Data Team • 12/01/2024
The vulnerability identified as CVE-2001-0830 affects 6tunnel version 0.08 and earlier implementations, representing a critical resource management flaw that exposes systems to denial of service attacks. This vulnerability specifically targets the socket handling mechanism within the 6tunnel application, which serves as a tunneling utility for IPv6 connections. The flaw manifests when the application fails to properly terminate network connections that are initiated by remote clients, creating a persistent resource leak within the system's network stack. This issue falls under the category of improper resource cleanup and can be classified as a CWE-404 weakness, which specifically addresses improper resource management leading to resource exhaustion.
The technical exploitation of this vulnerability involves a straightforward yet effective attack pattern where remote adversaries repeatedly establish connections to the vulnerable 6tunnel server and then immediately disconnect without proper cleanup. Each connection attempt creates a socket entry in the system's network connection table, and due to the flawed implementation, these entries remain active and consume system resources even after the client has disconnected. As attackers continue this cycle of connection and disconnection, the server's available socket resources gradually deplete until the system reaches its maximum connection limit, effectively preventing legitimate users from establishing new connections. This behavior constitutes a classic resource exhaustion attack pattern that can be mapped to ATT&CK technique T1499.004, which covers network denial of service attacks through resource exhaustion.
The operational impact of this vulnerability extends beyond simple service disruption, as it can severely compromise the availability and reliability of network services that depend on 6tunnel for IPv6 connectivity. Organizations relying on this tunneling software for network infrastructure may experience complete service outages, particularly in environments where IPv6 connectivity is essential for modern network operations. The vulnerability is particularly dangerous in high-traffic scenarios where multiple concurrent connections are expected, as the resource exhaustion occurs at a rate that can quickly overwhelm even moderately sized systems. The long-term consequences include potential system instability, increased administrative overhead for monitoring and recovery, and possible cascading failures in dependent network services that rely on stable connectivity.
Mitigation strategies for CVE-2001-0830 should prioritize immediate software updates to versions that address the socket management flaw, as this represents the most effective solution for resolving the root cause. System administrators should implement connection rate limiting and monitoring mechanisms to detect unusual connection patterns that may indicate exploitation attempts. Network segmentation and firewall rules can be configured to restrict access to 6tunnel services and limit the attack surface. Additionally, implementing proper socket timeout mechanisms and connection cleanup procedures can help prevent the accumulation of stale connections. Regular security audits and vulnerability assessments should be conducted to identify similar resource management flaws in other network applications, as this vulnerability demonstrates the critical importance of proper resource handling in network services. Organizations should also consider implementing intrusion detection systems that can identify and alert on connection flooding patterns that are characteristic of this type of denial of service attack.