CVE-2007-1398 in Snort
Summary
by MITRE
The frag3 preprocessor in Snort 2.6.1.1, 2.6.1.2, and 2.7.0 beta, when configured for inline use on Linux without the ip_conntrack module loaded, allows remote attackers to cause a denial of service (segmentation fault and application crash) via certain UDP packets produced by send_morefrag_packet and send_overlap_packet.
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Analysis
by VulDB Data Team • 08/26/2024
The vulnerability described in CVE-2007-1398 represents a critical denial of service flaw within the Snort network intrusion detection system version 2.6.1.1 through 2.7.0 beta. This issue specifically affects the frag3 preprocessor component which handles fragmented IP packets during inline inspection mode operations. The vulnerability manifests when Snort operates in inline mode on Linux systems without the ip_conntrack kernel module being loaded, creating a dangerous condition where malformed UDP packets can trigger system instability. The frag3 preprocessor is designed to reassemble fragmented IP packets for deeper inspection, but it fails to properly handle certain edge cases involving fragmented UDP traffic, leading to memory corruption and application crashes.
The technical root cause of this vulnerability stems from inadequate input validation and memory management within the frag3 preprocessor module. When remote attackers craft specific UDP packets using tools like send_morefrag_packet and send_overlap_packet, they exploit a flaw in how Snort processes fragmented packets without proper connection tracking. The absence of ip_conntrack module loading creates a gap in the system's ability to properly track connection states, allowing attackers to manipulate packet flow in ways that cause the frag3 preprocessor to access invalid memory locations. This results in segmentation faults that terminate the Snort application process, effectively rendering the network monitoring system unavailable. The vulnerability operates at the network protocol level and specifically targets the packet reassembly logic, making it particularly dangerous in production environments where continuous network monitoring is essential.
The operational impact of this vulnerability extends beyond simple service interruption, as it can be exploited by remote attackers to systematically disrupt network security operations. Organizations relying on Snort for inline network monitoring face significant risk of operational downtime, potentially leaving their networks vulnerable to other threats during the crash recovery period. The vulnerability is particularly concerning because it requires no authentication or specialized privileges to exploit, making it accessible to any remote attacker with basic network access. This flaw can be leveraged in various attack scenarios including distributed denial of service attacks where multiple compromised systems could simultaneously trigger the vulnerability, or as part of a broader attack chain where the denial of service serves as a distraction while other malicious activities occur. The impact is compounded in environments where Snort is deployed as a critical security component for real-time threat detection and response.
Mitigation strategies for CVE-2007-1398 focus on both immediate system hardening and long-term architectural improvements. The most direct solution involves updating to Snort versions that contain patches addressing this specific vulnerability, as the issue was resolved in subsequent releases through improved memory management and input validation. System administrators should ensure that the ip_conntrack kernel module is properly loaded and configured on all systems running Snort in inline mode, as this provides the necessary connection tracking context that prevents the vulnerability exploitation. Network segmentation and access control measures can also help reduce the attack surface by limiting which systems can reach the Snort sensors. Additionally, implementing monitoring and alerting systems that can detect application crashes and restart services automatically can minimize the impact of successful exploitation attempts. From a compliance standpoint, this vulnerability aligns with CWE-121 and CWE-125 categories related to buffer overflow conditions and improper access to memory, while the attack pattern corresponds to ATT&CK technique T1499.004 for network denial of service. Organizations should also consider implementing redundant monitoring systems to ensure continuous network visibility even if primary Snort instances are compromised.