CVE-2017-5202 in macOS
Summary
by MITRE
The ISO CLNS parser in tcpdump before 4.9.0 has a buffer overflow in print-isoclns.c:clnp_print().
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Analysis
by VulDB Data Team • 05/16/2026
The vulnerability identified as CVE-2017-5202 represents a critical buffer overflow flaw within the tcpdump network analysis tool that affects versions prior to 4.9.0. This issue resides in the ISO CLNS (Connectionless Network Service) parser implementation, specifically within the print-isoclns.c source file at the clnp_print() function. The buffer overflow occurs when tcpdump processes network packets containing ISO CLNS protocol data, creating a potential exploitation vector for malicious actors who could craft specially crafted packets to trigger the vulnerability.
The technical nature of this flaw stems from inadequate input validation and bounds checking within the CLNS packet parsing logic. When tcpdump encounters an ISO CLNS packet, the clnp_print() function attempts to process and display the packet contents without sufficient verification of buffer boundaries. This allows an attacker to construct packets with oversized or malformed CLNS data that exceeds the allocated buffer space, leading to memory corruption that can result in arbitrary code execution or application crash. The vulnerability manifests during network packet analysis operations where tcpdump processes captured network traffic containing ISO CLNS protocol information, making it particularly dangerous in network monitoring and security analysis environments.
The operational impact of this vulnerability extends beyond simple application instability to potentially enable remote code execution attacks against systems running vulnerable versions of tcpdump. Network security professionals and system administrators who rely on tcpdump for network traffic analysis, intrusion detection, and forensic investigations face significant risk when using affected versions. The vulnerability can be exploited through network packet injection attacks where malicious actors craft specially formatted ISO CLNS packets to trigger the buffer overflow condition. This creates a dangerous scenario for network monitoring systems that may be processing untrusted network traffic, potentially allowing attackers to compromise systems that are actively monitoring network activity.
Mitigation strategies for CVE-2017-5202 primarily involve upgrading to tcpdump version 4.9.0 or later, which contains the necessary patches to address the buffer overflow condition in the CLNS parser. System administrators should also implement network segmentation and access controls to limit exposure to potentially malicious traffic, while monitoring for anomalous network behavior that might indicate exploitation attempts. The vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and could potentially map to ATT&CK technique T1059.007 for remote code execution through network-based attack vectors. Organizations should also consider implementing network traffic filtering rules to prevent processing of suspicious ISO CLNS packets and maintain comprehensive logging of network analysis activities to detect potential exploitation attempts.