CVE-2016-7985 in macOS
Summary
by MITRE
The CALM FAST parser in tcpdump before 4.9.0 has a buffer overflow in print-calm-fast.c:calm_fast_print().
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Analysis
by VulDB Data Team • 05/16/2026
The vulnerability identified as CVE-2016-7985 represents a critical buffer overflow condition within the CALM FAST parser implementation in tcpdump versions prior to 4.9.0. This flaw exists specifically in the print-calm-fast.c source file at the calm_fast_print() function, where inadequate input validation and bounds checking allow maliciously crafted network packets to trigger memory corruption. The CALM FAST protocol is used for capturing and analyzing network traffic, making this vulnerability particularly dangerous as it could be exploited during normal packet processing operations. The buffer overflow occurs when the parser attempts to handle malformed CALM FAST protocol data without proper size verification, leading to potential memory overwrite conditions that could be leveraged by remote attackers.
The technical implementation of this vulnerability stems from improper handling of packet data structures within the tcpdump packet analysis framework. When tcpdump processes network traffic containing CALM FAST protocol headers, the calm_fast_print() function fails to validate the length of incoming data before attempting to copy it into fixed-size buffers. This classic buffer overflow pattern creates opportunities for attackers to inject malicious data that exceeds the allocated buffer boundaries, potentially overwriting adjacent memory regions including return addresses, function pointers, or other critical program state information. The vulnerability manifests during normal packet capture and analysis operations, making it particularly insidious as it can be triggered by legitimate network traffic without requiring special privileges or direct user interaction.
From an operational perspective, this vulnerability presents significant risks to network security monitoring systems that rely on tcpdump for packet analysis and intrusion detection. Attackers could exploit this flaw by crafting specially formatted CALM FAST protocol packets that, when processed by vulnerable tcpdump installations, would cause the application to crash or potentially execute arbitrary code. The impact extends beyond simple service disruption as the vulnerability could enable privilege escalation or remote code execution depending on the execution environment and system configuration. Organizations using tcpdump for network monitoring, forensic analysis, or security auditing would be particularly vulnerable since these systems often run with elevated privileges and process large volumes of network traffic. The vulnerability affects systems where tcpdump is used in network monitoring, security analysis, and packet capture scenarios, potentially compromising the integrity of security operations and forensic investigations.
Mitigation strategies for CVE-2016-7985 primarily focus on immediate version upgrades to tcpdump 4.9.0 or later, which contain the necessary patches to address the buffer overflow condition. System administrators should prioritize patching all tcpdump installations, particularly those deployed in security-sensitive environments or those handling untrusted network traffic. Additional defensive measures include implementing network segmentation and access controls to limit exposure to potentially malicious traffic, deploying intrusion detection systems that can identify and block malformed packets, and conducting thorough vulnerability assessments to identify all affected systems within the network infrastructure. The vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and could potentially map to ATT&CK technique T1059 for remote code execution through network protocol manipulation. Organizations should also consider implementing network traffic filtering rules that can identify and drop packets matching known patterns associated with this vulnerability to provide additional protection layers while patches are deployed.