CVE-2011-1935 in libpcap
Summary
by MITRE
pcap-linux.c in libpcap 1.1.1 before commit ea9432fabdf4b33cbc76d9437200e028f1c47c93 when snaplen is set may truncate packets, which might allow remote attackers to send arbitrary data while avoiding detection via crafted packets.
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Analysis
by VulDB Data Team • 11/28/2019
The vulnerability identified as CVE-2011-1935 resides within the libpcap library version 1.1.1, specifically in the pcap-linux.c component that handles packet capture operations on linux systems. This flaw manifests when the snaplen parameter is configured, which controls the maximum number of bytes captured from each packet. The issue represents a significant security concern as it enables a form of packet manipulation that can evade network monitoring systems. The vulnerability is particularly dangerous because it allows remote attackers to craft packets that appear benign while actually containing malicious data that goes undetected by network sniffing tools.
The technical mechanism behind this vulnerability involves the improper handling of packet truncation when the snaplen value is set to a specific configuration. In libpcap versions prior to the mentioned commit, the packet capture process would truncate packets based on the snaplen setting, but this truncation process contained a flaw that could be exploited. When snaplen was configured, the system would sometimes truncate packets in a manner that allowed attackers to inject arbitrary data payloads that would not be fully captured by the monitoring tools. This creates a scenario where network security systems relying on libpcap for packet capture could miss critical portions of malicious traffic, effectively providing a bypass mechanism for attackers.
The operational impact of this vulnerability extends beyond simple packet capture issues and represents a serious threat to network security monitoring capabilities. Network administrators and security professionals who rely on tools built on libpcap for intrusion detection, network forensics, and security monitoring may find their systems compromised. The vulnerability can be exploited remotely, meaning attackers do not need physical access to the network infrastructure to implement this attack. This makes it particularly dangerous in environments where network monitoring is critical for detecting malicious activity, as the system's ability to detect and respond to threats is significantly weakened.
This vulnerability maps to CWE-122, which describes "Heap-based Buffer Overflow" and aligns with ATT&CK technique T1046, "Network Service Scanning', and T1566, 'Phishing'. The weakness in packet truncation handling creates a condition where network traffic can be manipulated to avoid detection, which directly supports techniques for evading network monitoring systems. Organizations using network monitoring tools that depend on libpcap for packet capture should prioritize patching this vulnerability. The fix involves updating to a version of libpcap that includes the commit referenced in the CVE description, which properly addresses the packet truncation logic. System administrators should also consider implementing additional network monitoring measures and regular security assessments to ensure that packet capture systems remain effective against such evasion techniques. The vulnerability serves as a reminder of the critical importance of maintaining up-to-date network security tools and the potential consequences of outdated software in security monitoring environments.