CVE-2018-4002 in Smart Firewall
Summary
by MITRE
An exploitable denial-of-service vulnerability exists in the mdnscap binary of the CUJO Smart Firewall running firmware 7003. When parsing labels in mDNS packets, the firewall unsafely handles label compression pointers, leading to an uncontrolled recursion that eventually exhausts the stack, crashing the mdnscap process. An unauthenticated attacker can send an mDNS message to trigger this vulnerability.
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Analysis
by VulDB Data Team • 02/01/2024
The vulnerability identified as CVE-2018-4002 represents a critical denial-of-service flaw within the CUJO Smart Firewall's mdnscap binary component. This issue manifests specifically within the firmware version 7003, where the device's handling of mDNS packet labels contains a fundamental design flaw that can be exploited by remote attackers without authentication. The mdnscap process serves as a crucial network monitoring component responsible for capturing and processing multicast dns traffic, making it a prime target for exploitation in network security contexts.
The technical root cause of this vulnerability lies in the improper handling of label compression pointers during mDNS packet parsing operations. When the mdnscap binary encounters mDNS packets containing compressed labels, it fails to implement proper recursion depth checks or pointer validation mechanisms. This unsafe processing leads to uncontrolled recursion where the parser follows compression pointers without bounds, potentially creating infinite loops that consume stack memory rapidly. The vulnerability specifically targets the mDNS protocol implementation within the firewall's network stack, where label compression is a standard feature designed to reduce packet size by reusing previously transmitted label data.
The operational impact of this vulnerability extends beyond simple service disruption, as it can effectively render the CUJO Smart Firewall's network monitoring capabilities inoperative. When the mdnscap process crashes due to stack exhaustion, the firewall loses its ability to monitor and analyze multicast dns traffic, potentially compromising network visibility and security monitoring. This denial-of-service condition affects not only the device's primary function but also creates a potential attack surface where adversaries can repeatedly exploit the flaw to maintain service disruption. The vulnerability demonstrates a classic stack-based buffer overflow pattern that aligns with CWE-674, which specifically addresses uncontrolled recursion in software implementations.
From a cybersecurity perspective, this vulnerability exemplifies the risks associated with embedded network security devices that process network protocols without adequate input validation. The attack vector requires only sending a specially crafted mDNS packet to the firewall, making it particularly dangerous in environments where network traffic is not properly filtered or monitored. The lack of authentication requirements for exploitation means that any device connected to the network can potentially trigger the vulnerability, creating a widespread threat surface. This flaw also relates to ATT&CK technique T1499.002, which involves network denial-of-service attacks targeting network infrastructure components.
Mitigation strategies for CVE-2018-4002 should focus on firmware updates provided by the vendor, as the most effective solution addresses the root cause within the mdnscap binary implementation. Network administrators should also implement network segmentation to limit exposure to potential attackers and consider deploying additional monitoring solutions to detect unusual mDNS traffic patterns. The vulnerability highlights the importance of implementing proper recursion limits and pointer validation in network protocol handlers, particularly in embedded devices where resource constraints may limit the ability to implement comprehensive security measures. Organizations should also consider network access controls that can prevent unauthorized devices from injecting mDNS traffic into critical network segments.