CVE-2018-3985 in Smart Firewall
Summary
by MITRE
An exploitable double free vulnerability exists in the mdnscap binary of the CUJO Smart Firewall. When parsing mDNS packets, a memory space is freed twice if an invalid query name is encountered, leading to arbitrary code execution in the context of the mdnscap process. An unauthenticated attacker can send an mDNS message to trigger this vulnerability.
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Analysis
by VulDB Data Team • 08/03/2023
The CVE-2018-3985 vulnerability represents a critical double free memory corruption issue within the mdnscap component of the CUJO Smart Firewall device. This flaw manifests during the processing of malformed mDNS packets, specifically when the system encounters invalid query names that trigger improper memory management behavior. The vulnerability resides in the network packet parsing logic that handles multicast domain name service requests, which are fundamental to local network discovery and service announcement protocols. The mdnscap binary operates with elevated privileges to monitor and capture network traffic, making this vulnerability particularly dangerous as it could enable remote code execution within the firewall's operational context.
The technical implementation of this vulnerability follows a classic double free pattern where the same memory block gets deallocated twice during the processing of malformed mDNS responses. When the mdnscap binary receives an mDNS packet containing an invalid query name, the parsing routine fails to properly validate the input data structure before attempting memory deallocation operations. This improper handling causes the system to free the same memory region twice, creating a heap corruption condition that can be exploited by malicious actors. The vulnerability demonstrates characteristics consistent with CWE-415, which specifically addresses double free conditions in memory management operations. The flaw occurs in the context of network protocol parsing, where input validation is insufficient to handle malformed data structures that could lead to memory corruption.
The operational impact of this vulnerability extends beyond simple privilege escalation as it provides an unauthenticated attacker with a remote code execution vector directly targeting the firewall's core network monitoring functionality. Since the mdnscap process operates with elevated privileges and has direct access to network packet capture capabilities, successful exploitation could allow attackers to gain complete control over the device's network monitoring functions. This compromise would enable malicious actors to intercept, modify, or redirect network traffic passing through the firewall, potentially leading to man-in-the-middle attacks or complete network infiltration. The vulnerability's accessibility through unauthenticated mDNS messages means that any device on the local network could potentially exploit this flaw, making it particularly dangerous in shared network environments. Network security professionals should consider this vulnerability in relation to ATT&CK technique T1071.004 for application layer protocol usage and T1059.007 for command and scripting interpreter usage, as exploitation could enable further lateral movement or persistence within the network infrastructure.
Mitigation strategies for CVE-2018-3985 should focus on immediate firmware updates from the vendor to address the memory management flaw in the mdnscap binary. Network administrators should implement network segmentation and access controls to limit the exposure of affected devices to untrusted networks, while also monitoring for suspicious mDNS traffic patterns that could indicate exploitation attempts. The vulnerability highlights the importance of input validation in network protocol parsers and demonstrates the need for robust memory management practices in embedded security devices. Organizations should consider implementing network intrusion detection systems capable of identifying malformed mDNS packets and establishing network monitoring procedures to detect potential exploitation attempts. Additionally, regular security assessments of embedded network devices should include thorough analysis of protocol parsing components to identify similar memory corruption vulnerabilities that could be exploited in similar network security appliances.