CVE-2021-20988 in rcX RTOS
Summary
by MITRE • 05/13/2021
In Hilscher rcX RTOS versions prios to V2.1.14.1 the actual UDP packet length is not verified against the length indicated by the packet. This may lead to a denial of service of the affected device.
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Analysis
by VulDB Data Team • 05/16/2021
The vulnerability identified as CVE-2021-20988 affects Hilscher rcX RTOS systems prior to version V2.1.14.1, representing a critical security flaw in the network protocol implementation that could result in system disruption. This issue resides within the UDP packet processing mechanism where the system fails to validate the actual packet length against the length field specified in the packet header. The root cause stems from inadequate input validation procedures that allow malformed or oversized UDP packets to bypass normal processing checks, creating a potential vector for service disruption attacks.
The technical implementation flaw manifests when the real UDP packet size exceeds the value indicated in the packet's length field, leading to buffer overflow conditions or memory corruption within the RTOS network stack. This type of vulnerability falls under CWE-129, Input Validation, and specifically addresses improper validation of input boundaries that can result in memory safety issues. The absence of proper length verification creates a scenario where an attacker can craft malicious UDP packets that exploit the system's failure to enforce packet size constraints, potentially causing the device to crash or become unresponsive.
From an operational perspective, this vulnerability presents significant risks to industrial control systems and embedded devices that rely on Hilscher rcX RTOS for critical operations. The denial of service condition can impact manufacturing processes, automation systems, and network infrastructure that depend on continuous availability. Attackers could exploit this weakness to disrupt operations, causing production halts or system failures in environments where network reliability is paramount. The vulnerability is particularly concerning in industrial IoT deployments where devices may not have easy remote access for patching, making the impact more severe.
The security implications extend beyond simple service disruption, as this flaw could potentially be leveraged as a stepping stone for more sophisticated attacks within industrial control networks. The vulnerability aligns with ATT&CK technique T1499.004, Network Denial of Service, and represents a classic example of how insufficient input validation can create exploitable conditions in embedded systems. Organizations using affected Hilscher rcX devices should prioritize immediate remediation through firmware updates to version V2.1.14.1 or later, while implementing network segmentation and monitoring to detect anomalous UDP traffic patterns that might indicate exploitation attempts. Additionally, network administrators should consider implementing rate limiting and packet filtering rules to mitigate the risk of exploitation while awaiting official patches.