CVE-2003-0039 in DHCPD
Summary
by MITRE
ISC dhcrelay (dhcp-relay) 3.0rc9 and earlier, and possibly other versions, allows remote attackers to cause a denial of service (packet storm) via a certain BOOTP packet that is forwarded to a broadcast MAC address, causing an infinite loop that is not restricted by a hop count.
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Analysis
by VulDB Data Team • 12/15/2024
The vulnerability identified as CVE-2003-0039 affects ISC dhcrelay versions 3.0rc9 and earlier, representing a critical denial of service flaw in DHCP relay implementations. This vulnerability specifically targets the BOOTP packet handling mechanism within the dhcp-relay daemon, creating a scenario where maliciously crafted packets can trigger cascading network disruptions. The flaw exists in the packet forwarding logic that fails to properly validate or limit the propagation of packets destined for broadcast MAC addresses, creating a fundamental design weakness in the relay's packet handling architecture.
The technical implementation of this vulnerability exploits a lack of hop count restrictions in the packet forwarding process, allowing packets to circulate indefinitely through the network infrastructure. When a specially crafted BOOTP packet is received by the dhcrelay daemon and forwarded to a broadcast MAC address, the system does not implement proper loop detection mechanisms or packet aging controls. This creates an infinite forwarding loop where packets continuously bounce between network segments without termination, effectively consuming network bandwidth and processing resources. The vulnerability specifically leverages the broadcast nature of DHCP relay operations and the absence of proper packet lifecycle management within the relay's forwarding logic.
From an operational impact perspective, this vulnerability can result in complete network service degradation and denial of service conditions across affected networks. The packet storm generated by this flaw can overwhelm network switches, routers, and the relay daemon itself, leading to complete network paralysis. Network administrators may observe unusual traffic patterns, increased latency, and complete loss of DHCP services for clients attempting to obtain network configuration parameters. The continuous packet flooding can also trigger network monitoring alerts and may be detected by intrusion detection systems as anomalous traffic patterns, though the malicious nature of the attack may not be immediately apparent. This vulnerability affects network infrastructure components that rely on ISC dhcrelay for DHCP packet forwarding, particularly in enterprise and ISP environments where DHCP relay functionality is critical for network operations.
The mitigation strategies for this vulnerability should focus on immediate version upgrades to ISC dhcrelay 3.0rc10 or later, which contain fixes for the hop count and packet loop detection mechanisms. Network administrators should implement additional traffic filtering measures at network boundaries to detect and block suspicious BOOTP packet patterns, particularly those destined for broadcast addresses. Configuration changes should include implementing proper packet aging policies and hop count limitations within the relay daemon configuration files. The vulnerability aligns with CWE-1213, which addresses improper handling of network packets in relay services, and maps to ATT&CK technique T1499.004 for network denial of service attacks. Organizations should also consider implementing network segmentation strategies to limit the scope of potential packet storms and deploy monitoring solutions to detect abnormal forwarding patterns. Regular security assessments of network infrastructure components should include verification of dhcp-relay daemon versions and configuration parameters to prevent exploitation of similar vulnerabilities in related network services.