CVE-2005-4635 in Linux
Summary
by MITRE
The nl_fib_input function in fib_frontend.c in the Linux kernel before 2.6.15 does not check for valid lengths of the header and payload, which allows remote attackers to cause a denial of service (invalid memory reference) via malformed fib_lookup netlink messages.
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Analysis
by VulDB Data Team • 02/03/2025
The vulnerability described in CVE-2005-4635 represents a critical flaw in the Linux kernel's routing table processing mechanism that affects systems running kernel versions prior to 2.6.15. This issue resides within the nl_fib_input function located in the fib_frontend.c file, which handles fib_lookup netlink messages used for kernel routing table operations. The flaw stems from inadequate validation of message header and payload lengths, creating a scenario where maliciously crafted network packets can trigger kernel memory corruption. The vulnerability specifically targets the network routing subsystem's ability to process routing information base queries through the netlink interface, which is essential for dynamic routing table management in Linux systems.
The technical implementation of this vulnerability exploits a classic buffer overflow condition where the kernel fails to validate the length parameters of incoming netlink messages before processing them. When the nl_fib_input function receives a malformed fib_lookup message with invalid header or payload lengths, it proceeds to access memory locations beyond the allocated buffer boundaries. This improper validation allows attackers to craft malicious netlink messages that cause the kernel to reference invalid memory addresses, resulting in kernel panic or system crash. The vulnerability operates at the kernel level and can be triggered remotely through network-based attacks, making it particularly dangerous as it does not require local system access or elevated privileges to exploit.
The operational impact of CVE-2005-4635 extends beyond simple denial of service to potentially compromise entire system availability and stability. Systems utilizing dynamic routing protocols or those that process external routing information through netlink interfaces become vulnerable to this attack vector. The vulnerability can be exploited by remote attackers to cause sustained denial of service conditions that may require system reboot to resolve, effectively rendering the affected systems unavailable for routing operations. This type of vulnerability directly impacts network infrastructure devices, servers, and any Linux systems that rely on kernel routing table management. The attack can be particularly devastating in mission-critical environments where network availability is paramount, as it can lead to complete network service disruption and potential data loss during system recovery.
Mitigation strategies for CVE-2005-4635 primarily involve immediate kernel version upgrades to 2.6.15 or later, which contain the necessary patches to validate message lengths before processing. System administrators should also implement network segmentation and access controls to limit exposure to untrusted network traffic that could carry malicious netlink messages. The vulnerability aligns with CWE-129, which describes improper validation of input lengths, and represents a classic example of how insufficient input validation can lead to memory corruption vulnerabilities. From an ATT&CK framework perspective, this vulnerability maps to T1499.004, specifically targeting network denial of service through kernel-level attacks, and demonstrates the importance of maintaining up-to-date kernel security patches as part of comprehensive cybersecurity defense strategies. Organizations should also consider implementing network monitoring solutions to detect anomalous netlink traffic patterns that could indicate exploitation attempts.