CVE-2018-16451 in tcpdump
Summary
by MITRE
The SMB parser in tcpdump before 4.9.3 has buffer over-reads in print-smb.c:print_trans() for \MAILSLOT\BROWSE and \PIPE\LANMAN.
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Analysis
by VulDB Data Team • 12/03/2025
The vulnerability identified as CVE-2018-16451 represents a critical buffer over-read flaw within the Server Message Block (SMB) protocol parser of tcpdump version 4.9.2 and earlier. This issue manifests specifically within the print-smb.c module, where the print_trans() function fails to properly validate input data when processing SMB protocol messages. The vulnerability is particularly concerning as it affects the core packet analysis functionality of tcpdump, a widely used network protocol analyzer that operates at the network layer to capture and display packet data for troubleshooting and security analysis purposes.
The technical implementation of this vulnerability stems from inadequate bounds checking within the SMB parser's handling of specific SMB message types. When tcpdump encounters SMB traffic containing mailslot or named pipe messages, particularly those directed to \MAILSLOT\BROWSE and \PIPE\LANMAN endpoints, the print_trans() function attempts to read beyond the allocated buffer boundaries. This occurs because the parser does not properly verify the length of incoming SMB data structures before attempting to parse them, leading to memory access violations that can result in program crashes or potentially exploitable conditions. The vulnerability is classified under CWE-129 as an Improper Validation of Array Index, which specifically addresses the lack of proper bounds checking in array access operations.
The operational impact of this vulnerability extends beyond simple application instability to potentially compromise network security monitoring capabilities. When an attacker can cause tcpdump to crash through malformed SMB packets, it creates a denial of service condition that affects network administrators who rely on continuous packet capture for security monitoring and incident response. The vulnerability is particularly dangerous in environments where tcpdump is used for network traffic analysis, intrusion detection, or forensic investigations, as a successful exploitation could prevent security teams from capturing critical network data during security incidents. This represents a significant risk in enterprise environments where network visibility is crucial for maintaining security posture and compliance requirements.
The attack surface for this vulnerability is broad given tcpdump's widespread use across Unix-like systems and network monitoring environments. Network security tools, penetration testing frameworks, and system administration utilities that depend on tcpdump for packet analysis are all potentially affected. The vulnerability can be triggered by simply capturing network traffic containing maliciously crafted SMB packets, making it particularly dangerous in passive monitoring scenarios where administrators expect to be able to process all network traffic without risk of system compromise. From an adversarial perspective, this vulnerability aligns with ATT&CK technique T1046 for Network Service Scanning and T1490 for Inhibit System Recovery, as it can be used to disrupt network monitoring capabilities and potentially hide malicious activities from detection.
Mitigation strategies for CVE-2018-16451 primarily involve upgrading to tcpdump version 4.9.3 or later, which includes proper bounds checking and input validation for SMB message parsing. System administrators should also implement network segmentation and access controls to limit exposure to potentially malicious SMB traffic, while monitoring for unusual packet patterns that might indicate exploitation attempts. Additionally, organizations should consider implementing alternative network monitoring solutions or supplementing tcpdump with additional security controls to maintain visibility into network traffic even if the primary monitoring tool is compromised. The vulnerability serves as a reminder of the importance of regular security updates and proper input validation in network security tools that process untrusted data from network traffic.