CVE-2017-7670 in Traffic Control
Summary
by MITRE
The Traffic Router component of the incubating Apache Traffic Control project is vulnerable to a Slowloris style Denial of Service attack. TCP connections made on the configured DNS port will remain in the ESTABLISHED state until the client explicitly closes the connection or Traffic Router is restarted. If connections remain in the ESTABLISHED state indefinitely and accumulate in number to match the size of the thread pool dedicated to processing DNS requests, the thread pool becomes exhausted. Once the thread pool is exhausted, Traffic Router is unable to service any DNS request, regardless of transport protocol.
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Analysis
by VulDB Data Team • 10/24/2019
The vulnerability identified as CVE-2017-7670 affects the Traffic Router component within the Apache Traffic Control project, which serves as a critical infrastructure element for managing and directing network traffic. This component operates as a DNS server that handles incoming requests from clients seeking to resolve domain names, making it a prime target for denial of service attacks that can disrupt network services and compromise availability. The Apache Traffic Control project is designed to provide traffic management capabilities for large-scale web applications and content delivery networks, where the reliability and responsiveness of components like Traffic Router directly impacts the overall system performance and user experience.
The technical flaw resides in the Traffic Router's handling of TCP connections on the configured DNS port, where the system fails to properly manage connection lifecycle events. Specifically, when clients establish TCP connections to the DNS port, these connections remain in the ESTABLISHED state indefinitely without automatic timeout mechanisms or connection cleanup procedures. This behavior creates a persistent resource leak where each connection consumes system resources including memory and thread pool slots, effectively allowing malicious actors to exhaust available resources through sustained connection establishment without actual data transmission. The vulnerability manifests as a Slowloris-style attack pattern where attackers maintain numerous half-open connections to consume system resources, with the key distinction being that these connections remain in a fully established state rather than hanging in a half-open condition.
The operational impact of this vulnerability is severe and directly affects the availability of DNS services provided by the Traffic Router component. When the thread pool dedicated to processing DNS requests becomes exhausted due to accumulated connections in the ESTABLISHED state, the system reaches a complete service outage condition where no new DNS requests can be processed regardless of the transport protocol used. This creates a cascading effect that can disrupt all dependent services relying on DNS resolution, potentially affecting large-scale content delivery networks and web applications that depend on the Traffic Control infrastructure. The vulnerability is particularly dangerous because it can be exploited with minimal resources and sophisticated attack tools, making it an attractive target for attackers seeking to disrupt services without requiring significant computational power or advanced technical expertise.
Mitigation strategies for this vulnerability should focus on implementing proper connection timeout mechanisms and resource management policies within the Traffic Router component. System administrators should configure appropriate TCP connection timeouts to automatically close idle connections that remain in the ESTABLISHED state beyond acceptable thresholds, typically measured in minutes rather than hours or days. The implementation should align with industry standards such as those defined in CWE-400, which addresses the weakness of uncontrolled resource consumption, and should incorporate defensive programming practices to prevent resource exhaustion attacks. Organizations should also consider implementing rate limiting mechanisms to restrict the number of concurrent connections from individual clients and establish monitoring systems to detect unusual connection patterns that may indicate attempted exploitation. Additionally, regular security updates and patches should be applied to ensure that the Traffic Router component remains protected against known vulnerabilities, with network segmentation and access controls implemented to limit exposure to potential attackers. The solution should also include proper thread pool management with appropriate sizing and monitoring to prevent complete service exhaustion while maintaining adequate capacity for legitimate traffic processing.