CVE-2018-3963 in Smart Firewall
Summary
by MITRE
An exploitable command injection vulnerability exists in the DHCP daemon configuration of the CUJO Smart Firewall. When adding a new static DHCP address, its corresponding hostname is inserted into the dhcpd.conf file without prior sanitization, allowing for arbitrary execution of system commands. To trigger this vulnerability, an attacker can send a DHCP request message and set up the corresponding static DHCP entry.
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Analysis
by VulDB Data Team • 08/03/2023
The CVE-2018-3963 vulnerability represents a critical command injection flaw within the CUJO Smart Firewall's DHCP daemon implementation. This vulnerability resides in the network security device's configuration handling mechanism where the system fails to properly sanitize user-provided input before incorporating it into system commands. The affected device operates as a smart firewall that manages network traffic and DHCP services, making it a prime target for attackers seeking to compromise network infrastructure. The vulnerability specifically manifests when administrators or attackers attempt to add static DHCP entries to the device's configuration, creating a persistent attack surface that can be exploited without requiring physical access or elevated privileges.
The technical exploitation of this vulnerability occurs through the manipulation of hostname values during DHCP configuration processes. When a user submits a DHCP request with a specially crafted hostname, the system directly incorporates this unvalidated input into the dhcpd.conf configuration file without proper sanitization or escaping mechanisms. This design flaw allows attackers to inject malicious commands that execute with the privileges of the DHCP daemon process, typically running with elevated system permissions. The vulnerability falls under CWE-77 and CWE-94 categories, representing command injection and code injection weaknesses respectively, where user-controllable data flows directly into system command execution contexts. The ATT&CK framework categorizes this as a command and scripting interpreter execution technique, specifically targeting the execution of arbitrary commands on compromised systems.
The operational impact of this vulnerability extends beyond simple command execution, as it provides attackers with full control over the affected firewall device and potentially the entire network segment it protects. An attacker who successfully exploits this vulnerability can execute arbitrary system commands, potentially leading to complete system compromise, data exfiltration, or network reconnaissance activities. The attack requires minimal sophistication to execute, as it only requires sending a specially crafted DHCP request with a malicious hostname value, making it particularly dangerous in network environments where DHCP services are actively used. The vulnerability is particularly concerning because it affects network infrastructure devices that are typically considered secure and trusted components of the network architecture, potentially allowing attackers to establish persistent backdoors or escalate privileges within the network.
Mitigation strategies for CVE-2018-3963 should focus on immediate patching of the affected firmware versions, as well as implementing network segmentation and monitoring to detect anomalous DHCP traffic patterns. Organizations should also consider implementing network access controls to limit DHCP server access to authorized personnel only, and deploy intrusion detection systems to monitor for suspicious command execution patterns. The vulnerability demonstrates the critical importance of input validation and sanitization in network infrastructure devices, emphasizing the need for comprehensive security testing of all user-controllable inputs within system configuration processes. Additionally, administrators should implement regular security audits of network devices to identify similar vulnerabilities in other components that may be susceptible to command injection attacks.