CVE-2020-13986 in Contiki
Summary
by MITRE • 12/12/2020
An issue was discovered in Contiki through 3.0. An infinite loop exists in the uIP TCP/IP stack component when handling RPL extension headers of IPv6 network packets in rpl_remove_header in net/rpl/rpl-ext-header.c.
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Analysis
by VulDB Data Team • 12/16/2020
The vulnerability identified as CVE-2020-13986 represents a critical flaw in the Contiki operating system version 3.0 and earlier, specifically within its uIP TCP/IP stack implementation. This issue manifests as an infinite loop condition that occurs during the processing of RPL (Routing Protocol for Low-Power and Lossy Networks) extension headers in IPv6 packets. The affected component resides in the net/rpl/rpl-ext-header.c file where the rpl_remove_header function fails to properly handle certain malformed or unexpected header structures, leading to a denial of service condition that can render network operations completely unresponsive.
The technical root cause of this vulnerability stems from inadequate input validation and error handling within the RPL extension header processing logic. When the uIP stack encounters IPv6 packets containing RPL extension headers with specific malformed parameters, the rpl_remove_header function enters an infinite loop during header removal operations. This condition violates the fundamental principle of bounded execution time for network processing functions and creates a persistent denial of service scenario where the affected system becomes unresponsive to network traffic. The vulnerability is particularly concerning because it operates at the network protocol stack level, affecting the core communication capabilities of devices running Contiki.
From an operational perspective, this vulnerability poses significant risks to IoT and embedded systems that rely on Contiki for network connectivity. Devices such as sensor nodes, smart meters, and industrial control systems that utilize RPL for routing may become completely unresponsive when processing maliciously crafted IPv6 packets containing malformed RPL headers. The infinite loop condition prevents these systems from processing any further network traffic, effectively disabling their communication capabilities and potentially leading to complete system failure or requiring manual intervention for recovery. This vulnerability directly impacts the availability and reliability of networked embedded systems in critical infrastructure environments.
The security implications extend beyond simple denial of service as this vulnerability can be exploited by remote attackers to disrupt network operations without requiring authentication or privileged access. Network administrators and system operators should consider this issue in their risk assessments, particularly in environments where Contiki-based devices are deployed in mission-critical applications. The vulnerability aligns with CWE-835, which addresses infinite loops in software systems, and represents a classic example of how improper error handling in protocol implementations can lead to catastrophic system failures. Mitigation strategies should include immediate patching of Contiki to version 3.1 or later, where the infinite loop condition has been resolved through improved input validation and header processing logic.
Organizations deploying Contiki-based systems should implement network monitoring to detect unusual traffic patterns that might indicate exploitation attempts, as the vulnerability may be used as part of broader attack campaigns targeting IoT infrastructure. The remediation process involves updating the Contiki firmware to include proper bounds checking and header validation mechanisms that prevent the infinite loop condition from occurring. Additionally, network segmentation and access controls should be implemented to limit the potential impact of exploitation, as the vulnerability affects the fundamental networking capabilities of affected devices. This issue demonstrates the critical importance of robust error handling in embedded systems and highlights the need for comprehensive security testing of protocol stack implementations in resource-constrained environments.