CVE-2017-2889 in Circle with Disney
Summary
by MITRE
An exploitable Denial of Service vulnerability exists in the API daemon of Circle with Disney running firmware 2.0.1. A large amount of simultaneous TCP connections causes the APID daemon to repeatedly fork, causing the daemon to run out of memory and trigger a device reboot. An attacker needs network connectivity to the device to trigger this vulnerability.
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Analysis
by VulDB Data Team • 01/06/2023
The vulnerability identified as CVE-2017-2889 represents a critical denial of service weakness in the API daemon component of Circle with Disney smart home devices running firmware version 2.0.1. This flaw manifests through an insufficient resource management mechanism that fails to properly handle concurrent connection requests, creating a recursive process spawning behavior that ultimately exhausts system memory resources. The affected device operates under a typical embedded system architecture where the API daemon serves as the primary interface for communication between the device and external network clients, making it a prime target for exploitation through network-based attacks.
The technical root cause of this vulnerability stems from improper handling of TCP connection requests within the API daemon process. When an attacker establishes a large number of simultaneous TCP connections to the device, the daemon's process management logic triggers repeated forking operations to handle each incoming connection. This creates a fork bomb-like scenario where the system rapidly spawns new processes without adequate resource monitoring or connection limiting mechanisms. The vulnerability aligns with CWE-400, which categorizes unspecified resource exhaustion issues, and demonstrates poor implementation of resource management controls. The daemon fails to implement proper connection throttling, maximum connection limits, or process memory allocation controls that would prevent the system from becoming overwhelmed under high load conditions.
The operational impact of this vulnerability extends beyond simple service disruption to encompass complete device unavailability and potential denial of service for legitimate users. When the API daemon exhausts available memory through continuous forking, the device enters a reboot cycle that effectively renders it inoperable for the duration of the attack. This creates a cascading effect where legitimate users lose access to the smart home device functionality, potentially compromising security monitoring and home automation systems that depend on the device's continuous operation. The vulnerability operates at the network layer and affects the device's ability to maintain stable service, making it particularly dangerous in environments where continuous device availability is critical for security or operational purposes.
Mitigation strategies for this vulnerability should focus on implementing robust resource management controls and network access restrictions. Network administrators should deploy firewall rules to limit the number of concurrent connections to the device's API ports, effectively preventing the exploitation scenario from occurring. The device firmware should be updated to include proper connection limiting mechanisms and memory allocation controls that prevent excessive forking behavior. Additionally, implementing rate limiting and connection tracking features would help detect and block abnormal connection patterns that indicate potential exploitation attempts. From an ATT&CK framework perspective, this vulnerability maps to T1499.004 which covers network denial of service attacks, and organizations should consider implementing network monitoring solutions to detect unusual connection patterns that might indicate exploitation attempts. The recommended approach includes both immediate network-level protections and long-term firmware updates to address the underlying process management flaw.