CVE-2017-12997 in macOS
Summary
by MITRE
The LLDP parser in tcpdump before 4.9.2 could enter an infinite loop due to a bug in print-lldp.c:lldp_private_8021_print().
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Analysis
by VulDB Data Team • 12/05/2025
The vulnerability identified as CVE-2017-12997 resides within the Link Layer Discovery Protocol (LLDP) parser implementation of tcpdump version 4.9.1 and earlier. This issue manifests as an infinite loop condition that occurs when processing specially crafted LLDP packets, specifically within the print-lldp.c source file at the lldp_private_8021_print() function. The flaw represents a classic denial of service vulnerability that can be exploited by remote attackers to disrupt network monitoring and analysis operations that rely on tcpdump for packet inspection.
The technical root cause of this vulnerability stems from improper boundary checking within the LLDP packet parsing logic. When tcpdump encounters LLDP frames with malformed or excessively nested TLV (Type-Length-Value) structures, the parsing routine fails to properly validate the length fields of these elements, leading to a condition where the parser enters an infinite loop while attempting to process the malformed data. This behavior directly violates the principle of defensive programming and represents a CWE-835 vulnerability category, specifically related to infinite loops or iterations without proper termination conditions. The issue is particularly concerning because LLDP is commonly used in network infrastructure monitoring, making tcpdump a critical tool for network administrators who may unknowingly process malicious LLDP packets during routine network analysis.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise network monitoring infrastructure and availability. Network administrators who utilize tcpdump for traffic analysis, troubleshooting, or security monitoring may find their systems unresponsive or crash when processing affected LLDP packets, effectively rendering the monitoring tool ineffective during critical network events. This vulnerability can be exploited in various network scenarios including man-in-the-middle attacks, where an attacker sends malformed LLDP packets to disrupt network monitoring systems, or during network penetration testing where the tool's reliability is essential for accurate analysis. The vulnerability affects systems running tcpdump versions prior to 4.9.2, which were widely deployed across enterprise and security monitoring environments, making the potential impact substantial.
Mitigation strategies for CVE-2017-12997 primarily involve upgrading to tcpdump version 4.9.2 or later, which contains the necessary patches to address the infinite loop condition in the LLDP parser. Organizations should also implement network segmentation and access controls to limit exposure to potentially malicious LLDP traffic, while monitoring for unusual network behavior that might indicate exploitation attempts. The fix implemented in the patched version addresses the specific boundary checking issue within the lldp_private_8021_print() function, ensuring proper validation of TLV length fields and preventing the parser from entering infinite loops. Network security teams should also consider implementing additional monitoring and alerting mechanisms around tcpdump usage to detect potential exploitation attempts, as this vulnerability aligns with ATT&CK technique T1070.004 for Indicator Removal on Host and T1499.001 for Network Denial of Service, making it relevant to both defensive and offensive security operations.