CVE-2004-0816 in Linux
Summary
by MITRE
Integer underflow in the firewall logging rules for iptables in Linux before 2.6.8 allows remote attackers to cause a denial of service (application crash) via a malformed IP packet.
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Analysis
by VulDB Data Team • 11/26/2024
The vulnerability identified as CVE-2004-0816 represents a critical integer underflow condition within the iptables firewall implementation in Linux kernels prior to version 2.6.8. This flaw exists in the packet handling logic where the system fails to properly validate integer values during firewall logging operations, creating a scenario where maliciously crafted IP packets can trigger unexpected behavior in the kernel's network processing subsystem. The issue specifically affects the way iptables manages logging rules when processing incoming packets, particularly when dealing with certain packet size calculations that can result in negative integer values.
The technical exploitation of this vulnerability occurs when an attacker sends a malformed IP packet that causes the integer underflow condition during packet logging operations. When the iptables subsystem attempts to log the packet information, the improper integer handling results in a buffer overflow or memory corruption scenario that ultimately leads to a kernel panic or application crash. This type of vulnerability falls under the CWE-190 category of Integer Overflow or Wraparound, specifically manifesting as an integer underflow condition that occurs during the processing of network packets. The flaw demonstrates a classic example of inadequate input validation and integer arithmetic handling in kernel space code.
The operational impact of this vulnerability extends beyond simple denial of service, as it can potentially be leveraged to cause system instability or complete system crashes in environments where iptables firewall rules are actively processing network traffic. Network administrators who have not upgraded to kernel versions 2.6.8 or later face significant risk, as this vulnerability can be exploited remotely without requiring authentication or special privileges. The attack surface is particularly concerning in environments where firewalls are actively logging network traffic, as the underflow condition can be triggered simply by sending a single malformed packet to a system running vulnerable iptables code. This vulnerability aligns with ATT&CK technique T1499.004 for Network Denial of Service, as it specifically targets network infrastructure components to disrupt service availability.
Mitigation strategies for this vulnerability require immediate kernel upgrades to version 2.6.8 or later, where the integer underflow condition has been addressed through proper input validation and boundary checking in the iptables logging implementation. System administrators should also implement network segmentation and access control measures to limit exposure to potential attackers, while monitoring network traffic for unusual patterns that might indicate exploitation attempts. Additionally, organizations should conduct thorough vulnerability assessments to identify all systems running vulnerable kernel versions and ensure comprehensive patch management processes are in place to prevent similar issues from occurring in the future. The fix implemented in kernel 2.6.8 demonstrates proper defensive programming practices by ensuring integer values are properly validated before use in memory allocation calculations, thereby preventing the underflow condition that previously led to system crashes.