CVE-2017-13020 in macOS
Summary
by MITRE
The VTP parser in tcpdump before 4.9.2 has a buffer over-read in print-vtp.c:vtp_print().
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Analysis
by VulDB Data Team • 12/05/2025
The vulnerability identified as CVE-2017-13020 resides within the VLAN Trunking Protocol (VTP) parser implementation in tcpdump versions prior to 4.9.2. This issue manifests as a buffer over-read condition that occurs during the processing of VTP packets within the print-vtp.c source file at the vtp_print() function. The vulnerability represents a classic memory safety issue that can potentially lead to arbitrary code execution or system instability when tcpdump processes malformed VTP traffic.
The technical flaw stems from inadequate input validation and bounds checking within the VTP packet parsing logic. When tcpdump encounters VTP packets, the vtp_print() function attempts to read data from the packet buffer without sufficient verification of buffer boundaries. This allows an attacker to craft specially malformed VTP packets that can cause the parser to read beyond the allocated buffer space, potentially accessing uninitialized memory or memory belonging to other data structures within the application's address space. The vulnerability is classified under CWE-129 as an Improper Validation of Array Index, specifically manifesting as an out-of-bounds read condition.
The operational impact of this vulnerability extends beyond simple application crashes, as it can be exploited in network-based attack scenarios where an attacker controls network traffic. When exploited, the buffer over-read can lead to information disclosure, denial of service conditions, or potentially more severe consequences depending on the execution environment. The vulnerability is particularly concerning in network monitoring and security auditing contexts where tcpdump is commonly deployed to analyze network traffic. Attackers could leverage this flaw to cause tcpdump to crash or behave unpredictably, potentially disrupting network monitoring operations or creating opportunities for further exploitation.
Mitigation strategies for CVE-2017-13020 primarily involve upgrading to tcpdump version 4.9.2 or later, which includes proper bounds checking and input validation within the VTP parser. Network administrators should also implement network segmentation and access controls to limit exposure to potentially malicious VTP traffic. Additionally, monitoring for unusual VTP packet patterns and implementing intrusion detection systems can help identify potential exploitation attempts. From an ATT&CK framework perspective, this vulnerability aligns with techniques involving execution through a proxy and privilege escalation through local exploitation, making it a significant concern for network security operations. The fix implemented in version 4.9.2 demonstrates proper defensive programming practices including input validation, bounds checking, and memory safety mechanisms that align with industry best practices for preventing buffer overflow conditions.