CVE-2017-12985 in macOS
Summary
by MITRE
The IPv6 parser in tcpdump before 4.9.2 has a buffer over-read in print-ip6.c:ip6_print().
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Analysis
by VulDB Data Team • 12/04/2025
The vulnerability identified as CVE-2017-12985 represents a critical buffer over-read flaw within the IPv6 parsing functionality of tcpdump versions prior to 4.9.2. This issue manifests specifically within the print-ip6.c source file at the ip6_print() function, where improper boundary checking allows maliciously crafted IPv6 packets to trigger unauthorized memory access patterns. The flaw exists in the network protocol analysis tool that is widely used by security professionals and system administrators for packet inspection and network troubleshooting purposes.
The technical implementation of this vulnerability stems from inadequate input validation within the IPv6 header parsing logic. When tcpdump processes IPv6 packets containing malformed or specially crafted extension headers, the parser fails to properly validate the length fields of these headers before attempting to read memory regions that may extend beyond the allocated buffer boundaries. This over-read condition occurs because the code assumes that extension header lengths are properly formatted and within acceptable ranges without performing comprehensive bounds checking. The vulnerability is particularly concerning as it can be exploited through network traffic without requiring authentication or special privileges, making it a remote code execution risk.
The operational impact of this vulnerability extends beyond simple denial of service scenarios, as it can potentially enable attackers to extract sensitive information from memory locations adjacent to the parsed IPv6 headers. Network administrators who rely on tcpdump for security monitoring and incident response activities face significant risk when running vulnerable versions of the tool, as malicious actors could craft packets designed to trigger the over-read condition and potentially gain access to stack contents, heap data, or other memory segments that might contain credentials, session tokens, or other sensitive information. This makes the vulnerability particularly dangerous in environments where tcpdump is used for network monitoring, intrusion detection, or forensic analysis purposes.
Mitigation strategies for CVE-2017-12985 primarily focus on immediate version upgrades to tcpdump 4.9.2 or later, which contain the necessary patches to address the buffer over-read condition. System administrators should also implement network segmentation and access controls to limit exposure to potentially malicious traffic while applying patches. Additional defensive measures include configuring tcpdump with strict input validation parameters, implementing network monitoring rules to detect anomalous IPv6 packet patterns, and maintaining comprehensive logging of network traffic analysis activities. Organizations should also consider deploying network-based intrusion detection systems that can identify and block malformed IPv6 packets before they reach vulnerable tcpdump instances. This vulnerability aligns with CWE-129, which addresses improper validation of length fields, and represents a variant of the broader class of buffer over-read flaws that are frequently exploited in network protocol parsing contexts. The ATT&CK framework categorizes this vulnerability under T1059.007 for execution through command-line interfaces, as exploitation may involve crafting specific network traffic to trigger the vulnerable code path, and T1566 for initial access through network services that process packet data.