CVE-2004-0819 in OpenBSD
Summary
by MITRE
The bridge functionality in OpenBSD 3.4 and 3.5, when running a gateway configured as a bridging firewall with the link2 option for IPSec enabled, allows remote attackers to cause a denial of service (crash) via an ICMP echo (ping) packet.
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Analysis
by VulDB Data Team • 06/29/2019
The vulnerability identified as CVE-2004-0819 represents a critical denial of service flaw within the bridge functionality of OpenBSD versions 3.4 and 3.5. This issue specifically manifests when the operating system is configured as a gateway serving as a bridging firewall with IPSec enabled through the link2 option. The attack vector involves sending carefully crafted ICMP echo packets, commonly known as ping requests, which trigger a system crash and subsequent denial of service condition. The bridge functionality in question operates at the data link layer, facilitating network traffic forwarding between different network segments while maintaining the firewall protection mechanisms that are essential for network security.
The technical root cause of this vulnerability stems from inadequate input validation and error handling within the bridge implementation when processing ICMP echo packets in the specific context of IPSec-enabled gateway configurations. When the system receives an ICMP echo request while operating in bridging firewall mode with link2 option active, the packet processing routine fails to properly handle certain edge cases or malformed packet structures that occur during the IPSec packet processing pipeline. This failure results in a memory corruption condition or invalid pointer dereference that ultimately leads to the kernel crashing and the entire system becoming unresponsive. The vulnerability is classified under CWE-121, which deals with stack-based buffer overflow conditions, and more specifically aligns with CWE-125, indicating an out-of-bounds read that can lead to system instability. The flaw demonstrates how complex interactions between network protocols and security features can create unexpected crash conditions when proper boundary checking and error recovery mechanisms are absent.
The operational impact of this vulnerability extends beyond simple service disruption as it affects the fundamental stability and availability of network infrastructure components running OpenBSD in gateway configurations. Organizations relying on OpenBSD gateways for network segmentation and security enforcement face significant risks when these systems become unavailable due to remote exploitation. The attack requires minimal resources from the attacker who only needs to send ICMP echo packets to the affected system, making this a particularly dangerous vulnerability for network administrators who may not be aware of the specific configuration requirements that trigger the flaw. The vulnerability affects systems that are specifically configured with the link2 option for IPSec support, which represents a common setup for secure network gateways that require both bridging capabilities and IPSec security features. Network availability is compromised not only for the directly affected system but can also impact downstream network segments that depend on the gateway for connectivity and security enforcement.
Mitigation strategies for CVE-2004-0819 require immediate system updates to newer OpenBSD versions where the vulnerability has been addressed through proper input validation and error handling mechanisms. System administrators should prioritize upgrading their OpenBSD installations to versions that include patches for this specific bridge functionality issue. Additionally, network administrators can implement temporary workarounds such as disabling the link2 option for IPSec when not actively required, or applying firewall rules that limit ICMP traffic to reduce the attack surface. The remediation process should also include comprehensive network monitoring to detect anomalous ICMP traffic patterns that may indicate exploitation attempts. Organizations should follow the ATT&CK framework tactic T1499, which addresses network disruption and denial of service attacks, by implementing network segmentation and access controls that limit which systems can send ICMP packets to gateway devices. Regular vulnerability assessments and security audits should be conducted to identify similar configuration weaknesses in other network infrastructure components that may present analogous vulnerabilities. The incident response plan should include procedures for rapid system recovery and restoration of network services when such denial of service conditions occur, ensuring minimal impact on business continuity and network operations.