CVE-2019-1957 in IoT Field Network Director
Summary
by MITRE
A vulnerability in the web interface of Cisco IoT Field Network Director could allow an unauthenticated, remote attacker to trigger high CPU usage, resulting in a denial of service (DoS) condition on an affected device. The vulnerability is due to improper handling of Transport Layer Security (TLS) renegotiation requests. An attacker could exploit this vulnerability by sending renegotiation requests at a high rate. A successful exploit could increase the resource usage on the system, eventually leading to a DoS condition.
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Analysis
by VulDB Data Team • 11/21/2023
The vulnerability identified as CVE-2019-1957 resides within the web interface of Cisco IoT Field Network Director, a network management solution designed for IoT environments. This critical weakness stems from inadequate processing of Transport Layer Security renegotiation requests, creating a pathway for remote attackers to disrupt service availability. The affected device operates with a web interface that handles TLS connections, making it susceptible to exploitation through crafted TLS renegotiation sequences. The flaw represents a significant security gap in the platform's cryptographic handshake implementation, specifically in how it manages the renegotiation process that occurs during secure communications. This vulnerability directly impacts the operational integrity of IoT deployments that rely on Cisco's network director for device management and monitoring.
The technical flaw manifests through improper handling of TLS renegotiation requests, which are legitimate protocol features used to update security parameters during an active TLS session. When an attacker sends a high volume of renegotiation requests, the system fails to properly manage these repeated handshake attempts, leading to excessive CPU utilization. The vulnerability exploits the inherent design weakness in the TLS implementation where the system does not adequately rate-limit or process these requests, causing resource exhaustion. This improper state management creates a condition where the CPU becomes overwhelmed by processing these repeated requests, ultimately leading to system instability. The flaw aligns with CWE-227, which addresses weaknesses in cryptographic implementations, specifically targeting improper handling of TLS renegotiation. The vulnerability demonstrates characteristics consistent with CWE-400, indicating improper resource management through excessive CPU consumption.
The operational impact of this vulnerability extends beyond simple service disruption, creating potential business continuity risks for organizations relying on IoT Field Network Director for critical infrastructure management. An unauthenticated remote attacker can initiate a denial of service attack without requiring any credentials or prior access to the system, making it particularly dangerous in production environments. The high CPU usage resulting from the exploit can cause the device to become unresponsive, preventing legitimate users from accessing the web interface or managing connected IoT devices. This DoS condition directly affects the availability of network management capabilities, potentially leaving IoT deployments without proper oversight and control. The attack vector operates entirely over the network without requiring physical access, making it easily exploitable from anywhere on the internet. Organizations may experience extended downtime while attempting to restore normal operations, impacting operational efficiency and potentially affecting downstream IoT device functionality.
Mitigation strategies for CVE-2019-1957 should prioritize immediate patching of affected systems through Cisco's security advisory releases. Network administrators should implement rate-limiting measures on TLS renegotiation requests at the network perimeter to prevent excessive traffic patterns that could trigger the vulnerability. The implementation of intrusion detection systems capable of identifying abnormal TLS renegotiation activity can provide early warning of potential exploitation attempts. Organizations should also consider disabling TLS renegotiation entirely where possible, as this removes the attack surface entirely. Security teams should monitor system resource utilization patterns to detect anomalous CPU usage that may indicate exploitation attempts. Additionally, implementing network segmentation and access controls can limit the impact of successful attacks by restricting access to affected systems. The remediation approach should align with ATT&CK framework technique T1499, which addresses network denial of service attacks, requiring comprehensive defensive measures including both preventive and detective controls. Regular security assessments and vulnerability scanning should be conducted to identify similar weaknesses in related network infrastructure components.