CVE-2016-7164 in libtorrent
Summary
by MITRE
The construct function in puff.cpp in Libtorrent 1.1.0 allows remote torrent trackers to cause a denial of service (segmentation fault and crash) via a crafted GZIP response.
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Analysis
by VulDB Data Team • 08/25/2025
The vulnerability identified as CVE-2016-7164 resides within the Libtorrent library version 1.1.0, specifically within the construct function located in puff.cpp. This flaw represents a critical security issue that enables remote attackers to manipulate torrent trackers and induce system crashes through carefully crafted GZIP responses. The vulnerability operates at the intersection of network protocol handling and memory management, creating a pathway for denial of service attacks that can disrupt legitimate torrent operations.
The technical implementation of this vulnerability stems from insufficient input validation within the decompression routine of the Libtorrent library. When the construct function processes GZIP-encoded data from torrent trackers, it fails to properly validate the compressed data structure before attempting decompression. This oversight allows malicious actors to craft specially formatted GZIP responses that contain malformed data structures or unexpected compression sequences. The library's decompression algorithm, designed to handle standard GZIP formats, encounters these crafted inputs and attempts to process them without adequate bounds checking or error handling, resulting in memory corruption that manifests as segmentation faults.
From an operational perspective, this vulnerability creates significant risks for systems utilizing Libtorrent as their primary torrent handling library. The impact extends beyond simple service disruption to potentially compromise the availability of torrent-based services, including BitTorrent clients, seeders, and tracker systems. Attackers can exploit this weakness by controlling or compromising torrent trackers to send malicious GZIP responses to vulnerable Libtorrent implementations, causing crashes that may require manual intervention to restore service. The vulnerability affects any system running Libtorrent 1.1.0 or earlier versions, making it particularly concerning for widespread deployment scenarios.
The security implications align with CWE-129, which addresses improper validation of input boundaries, and demonstrates characteristics consistent with ATT&CK technique T1499.004, which involves network denial of service attacks. This vulnerability can be exploited in various attack scenarios including distributed denial of service campaigns targeting torrent infrastructure, where attackers leverage compromised trackers to systematically crash multiple client systems. The exploitation requires minimal technical expertise, making it particularly dangerous as it can be weaponized by threat actors with limited resources to create widespread service disruption.
Mitigation strategies for CVE-2016-7164 involve immediate upgrading to Libtorrent versions 1.1.1 or later, where the vulnerability has been addressed through enhanced input validation and improved decompression routines. System administrators should also implement network-level protections such as traffic filtering and monitoring for anomalous GZIP response patterns. Additional defensive measures include deploying intrusion detection systems that can identify suspicious torrent traffic patterns and implementing application-level sandboxing to limit the impact of potential crashes. Organizations should conduct comprehensive vulnerability assessments to identify all systems running affected Libtorrent versions and establish patch management procedures to ensure timely remediation of similar vulnerabilities.