CVE-2017-15133 in miekg-dns
Summary
by MITRE
A denial of service flaw was found in miekg-dns before 1.0.4. A remote attacker could use carefully timed TCP packets to block the DNS server from accepting new connections.
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Analysis
by VulDB Data Team • 12/31/2019
The vulnerability identified as CVE-2017-15133 represents a critical denial of service weakness in the miekg-dns library version 1.0.3 and earlier. This flaw specifically affects DNS server implementations that utilize the miekg-dns Go library for handling TCP-based DNS queries. The vulnerability stems from insufficient handling of TCP packet timing and connection management within the DNS server's processing pipeline, creating a scenario where an attacker can strategically manipulate connection establishment timing to disrupt normal service operations. The issue manifests when a remote attacker crafts and sends carefully timed TCP packets that exploit timing gaps in the server's connection acceptance mechanism, ultimately leading to a state where new connections cannot be properly established. This vulnerability directly impacts the availability aspect of the CIA triad by preventing legitimate users from accessing DNS services through the affected server.
The technical implementation of this flaw resides in how the miekg-dns library manages TCP connection lifecycle events and timing synchronization. When TCP packets arrive at specific intervals, the library's internal state machine fails to properly transition between connection states, creating a race condition that effectively blocks new connection attempts. The vulnerability is particularly insidious because it requires minimal resources from the attacker while producing significant operational impact. The flaw operates at the transport layer protocol handling level, where the timing of TCP packet arrivals triggers an internal buffer or state management issue that prevents the server from accepting subsequent connection requests. This creates a cascading effect where legitimate clients attempting to establish DNS connections encounter connection timeouts or rejection errors, effectively rendering the DNS service unavailable to authorized users. The vulnerability is classified under CWE-400 as an Uncontrolled Resource Consumption, specifically manifesting as a resource starvation attack against the TCP connection handling mechanism.
The operational impact of CVE-2017-15133 extends far beyond simple service disruption, as DNS servers form the foundational infrastructure for internet connectivity and domain resolution services. Organizations relying on miekg-dns for their DNS infrastructure face potential widespread service outages that can affect thousands of end users simultaneously. The attack vector allows for remote exploitation without requiring authentication or privileged access, making it particularly dangerous for public-facing DNS servers. The timing aspect of the attack means that even brief periods of sustained exploitation can cause significant operational disruption, as the server remains unresponsive to new connection requests until the affected state is cleared or the service is restarted. This vulnerability also impacts the reliability of critical internet infrastructure components, as DNS servers are often deployed in high-availability configurations where such disruption can cascade through dependent services and applications. The attack can be executed from anywhere on the internet, making it difficult to defend against through traditional network security measures, and the impact is immediate and severe for affected systems.
Mitigation strategies for CVE-2017-15133 require immediate implementation of the patched version 1.0.4 of the miekg-dns library, which addresses the TCP connection timing and state management issues. Organizations should conduct comprehensive vulnerability assessments to identify all systems utilizing the affected library version and prioritize remediation efforts accordingly. Network-level protections can include implementing TCP connection rate limiting and monitoring for unusual timing patterns in TCP packet sequences, though these measures are reactive and do not address the root cause. The most effective approach involves upgrading to the patched library version and implementing proper monitoring for connection state anomalies. System administrators should also consider implementing connection pooling strategies and connection timeout configurations that limit the impact of resource exhaustion attacks. Additionally, organizations should review their DNS server configurations to ensure proper handling of TCP connection limits and implement logging mechanisms that can detect unusual connection patterns. The remediation process should include thorough testing of the patched library in staging environments before deployment to production systems. This vulnerability highlights the importance of maintaining up-to-date security libraries and implementing robust security monitoring practices to detect and respond to timing-based attacks that exploit resource management weaknesses in critical infrastructure components. The attack pattern aligns with techniques described in the MITRE ATT&CK framework under the T1499 category for Network Denial of Service, specifically targeting resource exhaustion and service availability through protocol manipulation.