CVE-2002-0510 in Linux
Summary
by MITRE
The UDP implementation in Linux 2.4.x kernels keeps the IP Identification field at 0 for all non-fragmented packets, which could allow remote attackers to determine that a target system is running Linux.
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Analysis
by VulDB Data Team • 09/16/2025
The vulnerability described in CVE-2002-0510 represents a significant information disclosure issue within the Linux kernel's network stack implementation. This flaw specifically affects Linux 2.4.x kernel versions and manifests in how the kernel handles the IP Identification field in UDP packets. The IP Identification field is a crucial component of the Internet Protocol header that serves multiple purposes including packet fragmentation and reassembly. When this field remains consistently set to zero for all non-fragmented UDP packets, it creates a predictable pattern that can be exploited by remote attackers to infer system characteristics.
The technical nature of this vulnerability stems from the kernel's UDP implementation where it fails to properly initialize or randomize the IP Identification field for packets that do not require fragmentation. In standard network protocol implementations, the IP Identification field should contain a unique value for each packet to prevent issues during fragmentation and reassembly processes. However, the Linux 2.4.x kernel consistently sets this field to zero for non-fragmented packets, creating a distinctive behavioral signature that can be detected by external observers monitoring network traffic.
This vulnerability operates at the network protocol level and can be classified under CWE-200, which deals with information exposure. The operational impact of this flaw extends beyond simple information disclosure as it provides attackers with a method to fingerprint target systems. By analyzing network traffic patterns and identifying the consistent zero values in the IP Identification field, remote attackers can confidently determine that a target system is running a Linux kernel version affected by this vulnerability. This information gathering capability aligns with techniques described in the MITRE ATT&CK framework under T1018, which covers system network configuration discovery, and T1046, which covers network service scanning.
The implications of this vulnerability are particularly concerning in environments where network monitoring is active, as it provides attackers with a reliable method to identify Linux systems without requiring more sophisticated reconnaissance techniques. The predictable nature of the zero identification field means that attackers can quickly identify targets running vulnerable kernel versions and potentially use this information to plan more targeted attacks. This vulnerability demonstrates the importance of proper randomization in network protocol implementations and highlights how seemingly minor implementation details can have significant security implications.
Mitigation strategies for this vulnerability involve upgrading to patched kernel versions where the IP Identification field is properly initialized for all packets. System administrators should prioritize updating their Linux installations to versions that address this specific issue. Additionally, network monitoring solutions can be configured to alert on unusual patterns in IP Identification fields, though this represents a reactive approach rather than a direct fix. The vulnerability underscores the need for comprehensive security testing of network protocol implementations and demonstrates how adherence to security best practices in kernel development can prevent information disclosure issues that may aid attackers in their reconnaissance activities.