CVE-2009-0780 in OpenBSD
Summary
by MITRE
The aspath_prepend function in rde_attr.c in bgpd in OpenBSD 4.3 and 4.4 allows remote attackers to cause a denial of service (application crash) via an Autonomous System (AS) advertisement containing a long AS path.
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Analysis
by VulDB Data Team • 10/31/2018
The vulnerability identified as CVE-2009-0780 resides within the Border Gateway Protocol daemon implementation of OpenBSD versions 4.3 and 4.4. This flaw specifically affects the aspath_prepend function located in the rde_attr.c file, which is responsible for processing Autonomous System path attributes in BGP routing updates. The issue manifests when the bgpd process receives a malformed AS path advertisement that contains an excessively long sequence of autonomous system numbers, leading to a critical application crash that results in a denial of service condition for the entire BGP routing infrastructure.
The technical root cause of this vulnerability stems from inadequate input validation within the aspath_prepend function, which fails to properly handle or limit the length of AS path sequences during processing. When a remote attacker crafts a malicious BGP update message containing an abnormally long AS path, the function processes this input without sufficient bounds checking, causing memory corruption or buffer overflow conditions that ultimately lead to the bgpd process crashing. This represents a classic buffer overrun vulnerability that aligns with CWE-121, which describes unsafe use of a buffer, and more specifically CWE-129, which addresses insufficient bounds checking. The vulnerability operates at the network protocol level within the BGP routing subsystem, making it particularly dangerous as it can be exploited through standard network communication channels without requiring authentication or elevated privileges.
The operational impact of CVE-2009-0780 extends far beyond simple service disruption, as BGP is fundamental to internet routing operations across the global network infrastructure. When the bgpd daemon crashes due to this vulnerability, it causes complete disruption of BGP routing services on the affected OpenBSD system, potentially leading to widespread routing failures that can affect connectivity for multiple networks. The denial of service condition can persist until manual intervention occurs to restart the bgpd service or until the system is rebooted, creating significant operational challenges for network administrators who must respond to such incidents. This vulnerability particularly affects network operators who rely on OpenBSD for their border gateway routing functions, as it can be exploited by any remote attacker who can establish a BGP session with the vulnerable system, making it a critical security concern for internet service providers and network infrastructure operators.
Mitigation strategies for CVE-2009-0780 should prioritize immediate system updates and patches provided by OpenBSD developers, as version 4.5 and subsequent releases contain fixes addressing this specific vulnerability. Network administrators should implement BGP session filtering and path length validation measures at network boundaries to prevent malicious AS path advertisements from reaching vulnerable systems. The implementation of proper input validation and bounds checking within routing protocols represents a fundamental security practice that aligns with ATT&CK technique T1071.004, which covers application layer protocol traffic filtering. Additionally, organizations should consider implementing network segmentation and monitoring solutions that can detect abnormal BGP update patterns, as this vulnerability can be part of broader attack campaigns targeting network infrastructure. Regular security assessments and vulnerability scanning of network equipment should include verification of BGP implementation security, particularly focusing on path attribute handling and memory management functions to prevent similar issues from compromising network availability and stability.