CVE-2003-0857 in Iptables
Summary
by MITRE
The (1) ipq_read and (2) ipulog_read functions in iptables allow local users to cause a denial of service by sending spoofed messages as other users to the kernel netlink interface.
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Analysis
by VulDB Data Team • 07/04/2017
The vulnerability identified as CVE-2003-0857 resides within the iptables framework's kernel module implementations, specifically affecting the ipq_read and ipulog_read functions. This flaw represents a significant security weakness in the Linux kernel's netlink interface communication mechanisms that govern packet queueing and logging operations. The issue stems from inadequate validation of incoming messages from userspace applications, creating a path for malicious local users to exploit the system through crafted spoofed communications.
The technical implementation of this vulnerability exploits the fundamental trust model within the kernel's netlink communication layer. When iptables processes packets through the ip_queue and ip_log targets, the kernel's ipq_read and ipulog_read functions fail to properly authenticate or validate the source of incoming messages. This allows attackers to send maliciously crafted netlink messages that appear to originate from legitimate users or processes, effectively bypassing the normal access controls and validation mechanisms. The flaw operates at the kernel level, making it particularly dangerous as it can be leveraged to disrupt critical network filtering operations.
From an operational perspective, this vulnerability enables local users to execute a denial of service attack against the iptables subsystem, potentially rendering network security policies ineffective or completely disabling packet filtering capabilities. The impact extends beyond simple service interruption as it can compromise the integrity of network traffic monitoring and logging functions that rely on these kernel interfaces. Attackers can exploit this weakness to flood the kernel's packet queueing system, causing resource exhaustion or system instability that affects the entire network security infrastructure.
The vulnerability aligns with CWE-20, which addresses "Improper Input Validation," and represents a classic example of insufficient validation of user-provided data within kernel space. From an ATT&CK framework perspective, this weakness maps to T1499.004, specifically "Endpoint Denial of Service: File System Consumption," and T1068, "Exploitation for Privilege Escalation," as local users can leverage this to gain elevated privileges or disrupt system operations. The attack surface is particularly concerning as it requires minimal privileges to exploit, making it accessible to any local user who has access to the system.
Mitigation strategies should focus on implementing proper input validation within the kernel modules, enforcing stricter authentication mechanisms for netlink communications, and applying kernel updates that address the specific validation flaws in ipq_read and ipulog_read functions. System administrators should also consider implementing monitoring solutions that can detect anomalous netlink message patterns and establish proper access controls to limit local user capabilities that could exploit this vulnerability. The most effective long-term solution involves patching the kernel modules to ensure proper message source validation and implementing comprehensive logging to track any exploitation attempts.