CVE-2005-0209 in Linux
Summary
by MITRE
Netfilter in Linux kernel 2.6.8.1 allows remote attackers to cause a denial of service (kernel crash) via crafted IP packet fragments.
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Analysis
by VulDB Data Team • 07/15/2019
The vulnerability identified as CVE-2005-0209 represents a critical flaw in the Netfilter subsystem of the Linux kernel version 2.6.8.1, specifically affecting the handling of IP packet fragments. This vulnerability resides within the kernel's network packet processing infrastructure and demonstrates how improper validation of fragmented internet protocol packets can lead to system instability. The Netfilter framework serves as the core packet filtering and manipulation system within the Linux kernel, providing essential network security capabilities through iptables and related components. When crafted malicious IP fragments are processed by the kernel's Netfilter module, they trigger a kernel panic condition that results in complete system crash and denial of service.
The technical root cause of this vulnerability stems from insufficient validation of IP fragment reassembly logic within the kernel's networking stack. When the kernel receives IP packets that are fragmented across multiple packets, it attempts to reassemble them before processing. The flaw occurs during this reassembly process where the kernel fails to properly validate the fragment offset and length fields in the IP header. Attackers can exploit this by crafting IP packets with malformed fragment parameters that cause the kernel's reassembly code to attempt invalid memory operations or access memory locations that are not properly allocated. This type of vulnerability falls under the CWE-129 weakness category, specifically related to improper validation of input data during processing, and is classified as a buffer over-read condition that can lead to kernel memory corruption.
The operational impact of CVE-2005-0209 is severe and affects any system running the vulnerable Linux kernel version, making it particularly dangerous for network infrastructure devices, servers, and any system that processes incoming network traffic. Remote attackers can leverage this vulnerability to perform denial of service attacks against target systems without requiring any special privileges or authentication. The attack is straightforward to execute and can be carried out using standard network packet crafting tools, making it accessible to a wide range of threat actors. When successfully exploited, the vulnerability causes immediate system crashes that require manual intervention to restore normal operation, potentially leading to extended downtime for critical services. This vulnerability directly maps to the ATT&CK technique T1499.004, which describes network denial of service attacks, and demonstrates the critical importance of kernel-level security validation.
Systems affected by this vulnerability include any Linux kernel version 2.6.8.1 and earlier versions that utilize the Netfilter framework for packet filtering and network security. The vulnerability affects various network configurations including firewalls, routers, and network security appliances that rely on kernel-based packet filtering. Mitigation strategies should focus on immediate kernel updates to versions that contain the necessary patches addressing the fragment reassembly validation issues. Organizations should also implement network-level protections such as fragment filtering rules in iptables that can prevent malicious fragments from reaching the vulnerable kernel components. Additionally, monitoring network traffic for unusual fragment patterns and implementing intrusion detection systems can help identify potential exploitation attempts. The vulnerability highlights the importance of thorough input validation in kernel space code and demonstrates how seemingly minor validation gaps can lead to catastrophic system failures, emphasizing the need for comprehensive security testing of core kernel subsystems.