CVE-2019-1968 in NX-OS
Summary
by MITRE
A vulnerability in the NX-API feature of Cisco NX-OS Software could allow an unauthenticated, remote attacker to cause an NX-API system process to unexpectedly restart. The vulnerability is due to incorrect validation of the HTTP header of a request that is sent to the NX-API. An attacker could exploit this vulnerability by sending a crafted HTTP request to the NX-API on an affected device. A successful exploit could allow the attacker to cause a denial of service (DoS) condition in the NX-API service; however, the NX-OS device itself would still be available and passing network traffic. Note: The NX-API feature is disabled by default.
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Analysis
by VulDB Data Team • 12/11/2023
The vulnerability identified as CVE-2019-1968 resides within the NX-API feature of Cisco NX-OS Software, representing a critical security weakness that could be exploited by unauthenticated remote attackers to disrupt network operations. This flaw specifically targets the validation mechanisms implemented within the NX-API system process, which serves as a crucial interface for programmatically managing Cisco network devices. The NX-API functionality enables administrators to interact with network infrastructure through RESTful APIs, making it an essential component for network automation and management. However, the vulnerability manifests when the system fails to properly validate HTTP headers in incoming requests, creating an exploitable condition that could be leveraged by malicious actors to disrupt service availability. The vulnerability is particularly concerning because it operates at a fundamental level of the network device's operational framework, potentially compromising the reliability of network management systems that depend on NX-API functionality.
The technical implementation of this vulnerability stems from insufficient input validation within the NX-API request processing pipeline. When an HTTP request is received by the NX-API service, the system performs validation checks on various header fields to ensure proper request formatting and authentication. The flaw occurs when these validation routines fail to adequately sanitize or verify specific HTTP header components, allowing crafted malicious payloads to bypass normal security controls. Attackers can exploit this weakness by constructing specially formatted HTTP requests that manipulate header values in ways that trigger unexpected behavior within the NX-API system process. The improper validation creates a condition where the system process becomes unstable and subsequently restarts, leading to temporary disruption of the NX-API service. This restart process, while not causing complete device failure, effectively creates a denial of service condition for the NX-API functionality itself. The vulnerability demonstrates a classic weakness in input validation that aligns with CWE-20, which specifically addresses "Improper Input Validation" as a fundamental security flaw that can lead to various system disruptions and potential exploitation scenarios.
The operational impact of CVE-2019-1968 extends beyond simple service disruption to potentially compromise network management capabilities and operational efficiency. While the NX-OS device continues to function normally and maintain network traffic flow, the NX-API service becomes unavailable, preventing administrators from performing automated network management tasks through the API interface. This disruption can severely impact network operations that rely on programmatic access for configuration changes, monitoring, and troubleshooting activities. Network administrators who depend on automated workflows and script-based management tools would experience significant operational delays when the NX-API service becomes unavailable due to the vulnerability. The DoS condition affects the availability of network management interfaces that are critical for maintaining network health and responding to incidents, potentially forcing administrators to rely on alternative management methods such as command-line interfaces or physical device access. The vulnerability's impact is particularly significant in large-scale network environments where automated management through NX-API is essential for maintaining operational efficiency and reducing administrative overhead.
Mitigation strategies for CVE-2019-1968 should focus on both immediate defensive measures and long-term security enhancements. The most straightforward approach involves enabling proper input validation mechanisms within the NX-API service and ensuring that all HTTP header fields are properly sanitized before processing. Network administrators should consider disabling the NX-API feature entirely if it is not actively required, as the vulnerability exists even when the feature is present on the device. Cisco has released patches and updates to address this vulnerability, which should be applied immediately to all affected systems. Organizations should also implement network monitoring solutions that can detect anomalous HTTP request patterns that might indicate exploitation attempts. The security controls should include rate limiting and request validation mechanisms that can prevent the exploitation of input validation flaws. Additionally, implementing network segmentation and access controls can limit the potential impact of such vulnerabilities by restricting access to NX-API functionality to trusted administrative networks. This vulnerability serves as a reminder of the importance of proper input validation and the potential consequences of insufficient security controls in network management interfaces, aligning with ATT&CK technique T1499.002 for network denial of service attacks. Organizations should also consider implementing comprehensive vulnerability management programs that regularly assess and update network device configurations to prevent similar issues from occurring in the future.