CVE-2017-6729 in StarOS
Summary
by MITRE
A vulnerability in the Border Gateway Protocol (BGP) processing functionality of the Cisco StarOS operating system for Cisco ASR 5000 Series Routers and Cisco Virtualized Packet Core (VPC) Software could allow an unauthenticated, remote attacker to cause the BGP process on an affected system to reload, resulting in a denial of service (DoS) condition. This vulnerability affects the following products if they are running the Cisco StarOS operating system and BGP is enabled for the system: Cisco ASR 5000 Series Routers and Cisco Virtualized Packet Core Software. More Information: CSCvc44968. Known Affected Releases: 16.4.1 19.1.0 21.1.0 21.1.M0.65824. Known Fixed Releases: 21.3.A0.65902 21.2.A0.65905 21.1.b0.66164 21.1.V0.66014 21.1.R0.65898 21.1.M0.65894 21.1.0.66030 21.1.0.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 12/31/2020
The vulnerability identified as CVE-2017-6729 represents a critical denial of service weakness within the Border Gateway Protocol processing capabilities of Cisco StarOS operating system implementations. This flaw specifically targets Cisco ASR 5000 Series Routers and Cisco Virtualized Packet Core Software deployments where BGP functionality is actively enabled. The security issue stems from insufficient input validation mechanisms within the BGP processing module, creating an exploitable condition that allows remote attackers to manipulate the system's routing protocols. The vulnerability operates at the network protocol level, specifically affecting the core routing decision-making processes that govern how network traffic is forwarded across interconnected networks. According to the Cisco Security Advisory CSCvc44968, this weakness enables an unauthenticated attacker to trigger a complete reload of the BGP process, effectively disrupting the router's ability to maintain proper network connectivity and routing information exchange.
The technical exploitation of this vulnerability occurs through malformed BGP messages that are processed by the affected Cisco StarOS systems. When these specially crafted packets are received by the router's BGP daemon, the insufficient validation routines fail to properly handle the unexpected data structures, causing the BGP process to crash and subsequently reload. This behavior aligns with CWE-129, which describes issues related to insufficient validation of array indices, and reflects the broader category of input validation failures that commonly lead to process termination and service disruption. The flaw does not require authentication credentials or privileged access, making it particularly dangerous as it can be exploited from any network location with access to the affected router's BGP listening interface. The specific conditions that trigger this behavior involve the manipulation of BGP update messages, particularly those containing malformed attributes or path information that the system's parsing logic cannot properly interpret.
The operational impact of CVE-2017-6729 extends beyond simple service interruption to potentially compromise network stability and availability across large-scale deployments. When the BGP process reloads, all routing information maintained by the affected router becomes temporarily unavailable, causing routing disruptions that can cascade through interconnected networks. This vulnerability directly maps to the ATT&CK technique T1499.004, which involves network disruption through manipulation of routing protocols, and represents a significant threat to network infrastructure integrity. The DoS condition affects not only the immediate device but can also cause downstream network devices to experience routing instability as they attempt to recalculate paths around the affected router. Network operators may experience extended periods of service degradation while the system reinitializes its BGP processes and re-establishes peer connections, potentially leading to service interruptions for end users and applications dependent on the affected network paths.
Mitigation strategies for this vulnerability require immediate deployment of Cisco's released software patches and firmware updates to address the underlying BGP processing flaw. Network administrators should prioritize updating affected Cisco ASR 5000 Series Routers and VPC Software installations to the fixed releases including versions 21.3.A0.65902, 21.2.A0.65905, and other patched releases mentioned in the advisory. The implementation of network segmentation and access control measures can provide additional protection by limiting exposure of BGP listening interfaces to trusted networks only, reducing the attack surface available to potential remote attackers. Organizations should also implement monitoring solutions that can detect anomalous BGP traffic patterns and process restart events, enabling rapid response to exploitation attempts. The vulnerability demonstrates the importance of robust input validation in network protocol implementations and highlights the need for continuous security assessment of routing protocols. Additionally, network teams should consider implementing BGP security features such as Route Origin Authorization (ROA) and BGPsec to provide additional layers of protection against routing protocol manipulation attacks, ensuring that even if exploitation occurs, the broader network impact is minimized through proper validation of routing information authenticity.