CVE-2001-1400 in Linux
Summary
by MITRE
Unknown vulnerabilities in the UDP port allocation for Linux kernel before 2.2.19 could allow local users to cause a denial of service (deadlock).
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Analysis
by VulDB Data Team • 06/25/2021
The vulnerability identified as CVE-2001-1400 represents a critical flaw in the Linux kernel's implementation of User Datagram Protocol port allocation mechanisms prior to version 2.2.19. This issue stems from inadequate handling of UDP port assignment processes that creates potential deadlock conditions within the kernel's network subsystem. The vulnerability specifically affects systems running Linux kernels older than 2.2.19, where the kernel's UDP implementation contains race conditions and improper synchronization mechanisms during port allocation procedures. These flaws occur when multiple processes attempt to bind to UDP ports simultaneously, creating a scenario where kernel threads can become indefinitely blocked waiting for resources that will never be released. The root cause lies in the kernel's failure to properly manage concurrent access to port allocation tables and the absence of adequate locking mechanisms during critical sections of the UDP binding process. This vulnerability operates at the kernel level and directly impacts the network stack's ability to handle concurrent connections, making it particularly dangerous for systems that rely heavily on UDP-based services.
The technical exploitation of this vulnerability manifests through local users who can trigger the deadlock condition by creating specific patterns of UDP port binding requests. When multiple processes attempt to allocate UDP ports in a manner that creates circular dependencies or resource contention, the kernel's locking mechanisms fail to resolve the situation properly, resulting in a complete system deadlock. The flaw is classified as a race condition under CWE-362, specifically involving concurrent execution issues where the lack of proper synchronization leads to unpredictable system behavior. The vulnerability also maps to ATT&CK technique T1499.004, which covers network disruption attacks through resource exhaustion and system locking mechanisms. The UDP port allocation process in affected kernels does not implement proper timeout mechanisms or deadlock detection, allowing malicious or accidental concurrent access patterns to bring the entire system network functionality to a halt.
The operational impact of CVE-2001-1400 extends beyond simple denial of service conditions to potentially compromise entire system availability and network services. Systems running vulnerable kernel versions become susceptible to complete network stack failures where no UDP traffic can be processed until the system is rebooted. This vulnerability affects any service or application that relies on UDP port binding, including DNS servers, NTP daemons, VoIP applications, and various network monitoring tools. The vulnerability is particularly concerning in server environments where multiple applications might attempt to bind to UDP ports simultaneously, creating an environment where the system becomes unresponsive to network traffic. Network administrators may observe complete loss of UDP connectivity without any clear indication of the underlying kernel-level issue, making troubleshooting difficult and time-consuming. The vulnerability also impacts system stability in high-traffic scenarios where concurrent port allocation requests are common, potentially leading to extended downtime for critical network services. Organizations with legacy systems running affected kernel versions face significant operational risks, as the vulnerability can be triggered by normal system operations rather than malicious attacks.
Mitigation strategies for CVE-2001-1400 focus primarily on kernel version upgrades to 2.2.19 or later, which contain the necessary fixes for proper UDP port allocation synchronization. System administrators should prioritize immediate patching of all affected systems, particularly those running server workloads that handle high volumes of UDP traffic. The kernel patches address the underlying race conditions by implementing proper locking mechanisms and timeout procedures during port allocation processes, preventing the deadlock scenarios that previously occurred. Organizations should also implement monitoring solutions to detect unusual patterns of UDP port binding that might indicate attempted exploitation of this vulnerability. Network segmentation and access controls can help limit local user privileges that could potentially trigger the vulnerability. Additionally, system administrators should consider implementing automated patch management solutions to ensure all systems remain current with security updates. The vulnerability demonstrates the critical importance of maintaining up-to-date kernel versions and highlights the risks associated with running legacy systems that may contain unpatched security flaws. Regular security assessments and vulnerability scanning should include checks for this specific kernel vulnerability to ensure comprehensive system protection against similar issues.