CVE-2020-1939 in NuttX
Summary
by MITRE
The Apache NuttX (Incubating) project provides an optional separate "apps" repository which contains various optional components and example programs. One of these, ftpd, had a NULL pointer dereference bug. The NuttX RTOS itself is not affected. Users of the optional apps repository are affected only if they have enabled ftpd. Versions 6.15 to 8.2 are affected.
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Analysis
by VulDB Data Team • 05/13/2020
The Apache NuttX RTOS project represents a critical embedded operating system framework designed for resource-constrained environments including IoT devices and embedded systems. This particular vulnerability exists within the optional "apps" repository that contains supplementary components and example programs beyond the core RTOS functionality. The ftpd component within this repository implements a File Transfer Protocol server functionality that allows remote file operations over network connections. The vulnerability specifically impacts users who have explicitly enabled this optional ftpd service within their NuttX configurations, creating a targeted attack surface that does not affect the base RTOS itself. This distinction is crucial for security assessments as it indicates the vulnerability is contained within the application layer rather than the kernel or core operating system components.
The technical flaw manifests as a NULL pointer dereference condition that occurs when the ftpd service processes certain network requests or file operations. This type of vulnerability typically arises when the software attempts to access memory through a pointer that has not been properly initialized or has been set to NULL. According to CWE classification, this vulnerability maps to CWE-476 which specifically addresses NULL pointer dereference conditions in software implementations. The flaw represents a classic denial-of-service vulnerability where an attacker can craft malicious network requests that cause the ftpd service to crash or terminate unexpectedly. The vulnerability affects all versions within the 6.15 to 8.2 range, indicating a prolonged period during which the issue remained unpatched in the software lifecycle.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise system availability in embedded environments where reliable network services are critical. In IoT deployments or industrial control systems where NuttX serves as the underlying operating system, an attacker could exploit this vulnerability to cause service outages that might affect device functionality or data access capabilities. The attack surface is limited to systems that have explicitly enabled the ftpd service, but this restriction does not diminish the potential impact in environments where network-based file access is essential. The vulnerability demonstrates the importance of thorough security testing for optional components that may be enabled in production environments, as these components often receive less rigorous security scrutiny than core system functions.
Mitigation strategies for this vulnerability should prioritize immediate patching of affected versions to address the NULL pointer dereference issue. System administrators and developers should conduct comprehensive inventory assessments to identify all NuttX installations that have enabled the ftpd service and ensure these systems receive updates. The ATT&CK framework categorizes this vulnerability under T1499.004 which deals with network denial-of-service attacks, highlighting the importance of network service hardening and monitoring. Organizations should implement network segmentation and access controls to limit exposure of systems running the affected ftpd service. Additionally, regular security audits of optional components within embedded systems are recommended to identify and remediate similar vulnerabilities before they can be exploited in operational environments.