CVE-2018-16596 in Internet Box Light
Summary
by MITRE
A stack-based buffer overflow in the LAN UPnP service running on UDP port 1900 of Swisscom Internet-Box (2, Standard, and Plus) prior to v09.04.00 and Internet-Box light prior to v08.05.02 allows remote code execution. No authentication is required to exploit this vulnerability. Sending a simple UDP packet to port 1900 allows an attacker to execute code on a remote device. However, this is only possible if the attacker is inside the LAN. Because of ASLR, the success rate is not 100% and leads instead to a DoS of the UPnP service. The remaining functionality of the Internet Box is not affected. A reboot of the Internet Box is necessary to attempt the exploit again.
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Analysis
by VulDB Data Team • 04/21/2020
This vulnerability represents a critical stack-based buffer overflow within the Universal Plug and Play UPnP service implementation on Swisscom Internet-Box devices. The flaw exists in the handling of UDP packets received on port 1900, which is the standard port used for UPnP discovery and communication protocols. The vulnerability affects multiple variants of the Swisscom Internet-Box including the 2, Standard, and Plus models with firmware versions prior to v09.04.00, as well as the Internet-Box light model with versions prior to v08.05.02. The absence of authentication requirements for exploitation makes this particularly dangerous as any device within the local network can potentially leverage this vulnerability without additional credentials or access privileges.
The technical nature of this vulnerability stems from improper input validation within the UPnP service implementation where incoming UDP packets are not adequately bounds-checked before being processed. When a malformed UDP packet is sent to port 1900, the service fails to validate the packet size or structure, allowing an attacker to overflow the allocated stack buffer and potentially overwrite adjacent memory locations. This type of vulnerability maps directly to CWE-121 Stack-based Buffer Overflow, which is classified as a fundamental memory safety issue in software development practices. The exploitation mechanism relies on the attacker sending a specifically crafted UDP packet that triggers the buffer overflow condition, potentially leading to arbitrary code execution within the context of the UPnP service process.
The operational impact of this vulnerability is significant within local network environments where attackers can leverage the lack of authentication requirements to gain unauthorized code execution capabilities. While the attack vector requires local network access, this limitation does not diminish the severity since most home and office networks are not adequately segmented to prevent such lateral movement. The presence of ASLR (Address Space Layout Randomization) in the target system introduces a mitigating factor that reduces exploitation reliability to approximately 50% in typical scenarios, as the randomization of memory addresses makes it difficult to predict the exact memory layout required for successful code execution. This partial mitigation results in a Denial of Service condition rather than guaranteed remote code execution, though the potential for exploitation remains substantial.
The security implications extend beyond simple DoS conditions as the vulnerability represents a persistent threat to network integrity and device control. Even with the reduced exploitation success rate, the potential for repeated attempts makes this a viable attack vector for persistent threat actors who can continuously probe the system. The requirement for a device reboot to attempt exploitation again indicates that the vulnerability can be repeatedly targeted without permanent system damage, allowing for sustained attack campaigns. Organizations should consider this vulnerability in the context of the MITRE ATT&CK framework, specifically under the T1059.007 technique for Command and Scripting Interpreter and T1068 for Exploitation for Privilege Escalation, as the vulnerability enables unauthorized execution of code within the device's operating environment. The attack surface is particularly concerning for network infrastructure devices that are often overlooked in traditional security assessments, as these devices frequently run with elevated privileges and serve as central points of network communication.