CVE-2015-5685 in Bootstrap
Summary
by MITRE
The lazy_bdecode function in BitTorrent DHT bootstrap server (bootstrap-dht ) allows remote attackers to execute arbitrary code via a crafted packet, related to "improper indexing."
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Analysis
by VulDB Data Team • 09/21/2018
The CVE-2015-5685 vulnerability represents a critical remote code execution flaw discovered in the BitTorrent DHT bootstrap server implementation known as bootstrap-dht. This vulnerability specifically targets the lazy_bdecode function which is responsible for parsing and decoding data structures within the DHT protocol. The issue arises from improper indexing operations that occur during the decoding process, creating a pathway for malicious actors to inject and execute arbitrary code on affected systems. The vulnerability exists within the core protocol handling mechanism of BitTorrent's distributed hash table system, making it particularly dangerous as it affects the fundamental infrastructure that enables peer-to-peer file sharing networks to function.
The technical exploitation of this vulnerability occurs when a remote attacker crafts a malicious packet that triggers the lazy_bdecode function with malformed data structures. The improper indexing mechanism within this function fails to properly validate array bounds or data structure integrity, allowing attackers to manipulate memory access patterns and potentially overwrite critical program variables or execute arbitrary machine code. This type of vulnerability falls under the CWE-129 category of Improper Validation of Array Index, which specifically addresses issues where programs fail to validate that array indices are within valid bounds. The attack vector leverages the DHT bootstrap process where nodes communicate to establish network connectivity, making the vulnerability particularly insidious as it can be triggered simply by connecting to a malicious bootstrap server.
The operational impact of CVE-2015-5685 extends far beyond individual system compromise, as it affects the entire BitTorrent ecosystem and potentially exposes thousands of nodes to remote code execution. When exploited, this vulnerability allows attackers to gain complete control over affected systems, enabling them to install malware, steal sensitive data, or use compromised nodes as part of botnets for further attacks. The distributed nature of BitTorrent networks means that a single compromised bootstrap server can potentially affect numerous peers across the network, creating a cascading effect of compromise. This vulnerability directly maps to ATT&CK technique T1059.007 for Command and Scripting Interpreter: PowerShell and T1071.004 for Application Layer Protocol: DNS, as attackers could leverage the compromised nodes to execute commands or establish command and control channels. The attack could be particularly devastating in environments where BitTorrent clients are used for legitimate business purposes, as it could lead to complete network compromise.
Mitigation strategies for CVE-2015-5685 require immediate patching of affected bootstrap-dht implementations, with administrators ensuring all systems running BitTorrent DHT bootstrap services receive updates from their vendors. Network administrators should implement strict firewall rules to limit access to DHT bootstrap servers and consider disabling DHT functionality in BitTorrent clients when not required. The vulnerability highlights the importance of proper input validation and memory safety practices in network protocol implementations, particularly in systems handling untrusted data from peers. Organizations should also consider implementing network monitoring to detect unusual DHT traffic patterns that might indicate exploitation attempts. Additionally, security teams should conduct thorough vulnerability assessments of all BitTorrent-related software components and ensure that proper bounds checking and input validation mechanisms are implemented in all data parsing functions to prevent similar issues from occurring in the future.