CVE-2016-7931 in macOS
Summary
by MITRE
The MPLS parser in tcpdump before 4.9.0 has a buffer overflow in print-mpls.c:mpls_print().
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Analysis
by VulDB Data Team • 05/16/2026
The vulnerability identified as CVE-2016-7931 represents a critical buffer overflow flaw within the multiprotocol label switching mpls parser of tcpdump version 4.9.0 and earlier. This issue resides in the print-mpls.c source file at the mpls_print() function, where insufficient input validation and boundary checking allows maliciously crafted packet data to trigger memory corruption. The vulnerability specifically affects network packet analysis tools that process mpls labeled packets, creating a potential attack surface for remote exploitation. The buffer overflow occurs when tcpdump attempts to parse mpls headers that exceed expected data structures, leading to unauthorized memory access patterns that can result in arbitrary code execution or application crashes.
The technical implementation of this vulnerability stems from inadequate bounds checking during packet header parsing operations. When tcpdump encounters mpls packets with malformed or oversized label stacks, the mpls_print() function fails to validate the incoming data against predetermined buffer limits. This flaw aligns with CWE-121, which categorizes stack-based buffer overflow conditions, and CWE-787, which addresses out-of-bounds write operations. The vulnerability exploits the fundamental principle that network protocol parsers must validate all input data before processing, particularly when handling variable-length fields within packet headers. Attackers can craft specially formatted mpls packets that cause the parser to write beyond allocated memory boundaries, potentially overwriting adjacent memory regions with controlled data.
The operational impact of CVE-2016-7931 extends beyond simple application crashes to encompass potential system compromise and denial of service scenarios. Network monitoring systems that rely on tcpdump for packet inspection become vulnerable to remote exploitation, allowing attackers to execute arbitrary code on systems running affected versions. This presents significant risk to network security operations centers where tcpdump is commonly deployed for traffic analysis and intrusion detection. The vulnerability can be exploited through network traffic injection, where attackers send malformed mpls packets to systems running vulnerable tcpdump versions. This attack vector maps to ATT&CK technique T1059.007, which covers command and scripting interpreter execution, and T1499.004, which involves network disruption through service availability attacks.
Mitigation strategies for this vulnerability require immediate patching of tcpdump installations to versions 4.9.0 or later, which contain the necessary buffer overflow protections. Organizations should implement network segmentation and access controls to limit exposure of systems running tcpdump to untrusted network traffic. Additional defensive measures include deploying network intrusion detection systems that can identify and block malformed mpls packet patterns, implementing proper input validation at network boundaries, and conducting regular vulnerability assessments of network monitoring tools. The fix implemented in tcpdump 4.9.0 addresses the root cause by introducing proper bounds checking and memory allocation validation before processing mpls header data. Security teams should also consider implementing network monitoring solutions that can detect anomalous packet behavior indicative of exploitation attempts, as well as maintaining comprehensive network traffic logging for forensic analysis purposes.