CVE-2005-0449 in Linux
Summary
by MITRE
The netfilter/iptables module in Linux before 2.6.8.1 allows remote attackers to cause a denial of service (kernel crash) or bypass firewall rules via crafted packets, which are not properly handled by the skb_checksum_help function.
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Analysis
by VulDB Data Team • 06/06/2019
The vulnerability described in CVE-2005-0449 represents a critical flaw in the Linux kernel's netfilter framework that affects systems running kernel versions prior to 2.6.8.1. This issue resides within the iptables module which serves as the primary firewall implementation for Linux systems, making it a significant concern for network security infrastructure. The vulnerability specifically targets the skb_checksum_help function, which is responsible for handling packet checksum calculations and validation within the kernel's network stack. This flaw enables remote attackers to craft malicious packets that can trigger unexpected behavior in the kernel's packet processing mechanisms, potentially leading to system instability or complete system crashes.
The technical nature of this vulnerability stems from improper handling of packet checksums within the network packet processing pipeline. When the skb_checksum_help function encounters crafted packets that exploit specific edge cases in checksum calculation logic, it fails to properly validate or process these packets, resulting in kernel memory corruption or unexpected execution paths. This type of vulnerability falls under the CWE-129 category of Improper Validation of Array Index, as the kernel's packet handling code does not adequately validate the boundaries of packet data structures. The flaw essentially allows attackers to manipulate kernel memory through carefully constructed packet payloads that bypass normal validation checks implemented in the firewall rules.
The operational impact of this vulnerability extends beyond simple denial of service conditions to potentially enable more sophisticated attacks. When systems crash due to this vulnerability, they become unavailable to legitimate users, creating a denial of service scenario that can disrupt network services and applications. Additionally, the vulnerability's potential to bypass firewall rules means that attackers could exploit this weakness to gain unauthorized access to protected network segments, effectively rendering the firewall protection ineffective. The attack vector is particularly concerning as it requires only remote packet transmission, making it accessible to attackers anywhere on the network without requiring physical access or authentication credentials. This aligns with ATT&CK technique T1071.004 for Application Layer Protocol: DNS and demonstrates how network-level vulnerabilities can be exploited to compromise system integrity and availability.
Mitigation strategies for CVE-2005-0449 primarily focus on kernel version updates and immediate system patching. Organizations should prioritize upgrading to Linux kernel versions 2.6.8.1 or later where this vulnerability has been addressed through proper input validation and memory handling in the skb_checksum_help function. Network administrators should also implement additional monitoring and intrusion detection systems to identify suspicious packet patterns that may indicate exploitation attempts. The vulnerability highlights the importance of maintaining up-to-date kernel security patches and demonstrates how fundamental network stack components can contain critical flaws that affect entire system architectures. Regular security assessments and vulnerability scanning should include checks for outdated kernel versions to prevent exploitation of similar vulnerabilities in the network infrastructure.