CVE-2008-0646 in Deluge
Summary
by MITRE
The bdecode_recursive function in include/libtorrent/bencode.hpp in Rasterbar Software libtorrent before 0.12.1, as used in Deluge before 0.5.8.3 and other products, allows context-dependent attackers to cause a denial of service (stack exhaustion and crash) via a crafted bencoded message.
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Analysis
by VulDB Data Team • 08/04/2019
The vulnerability described in CVE-2008-0646 represents a critical stack exhaustion issue within the libtorrent library implementation that affects numerous peer-to-peer applications including Deluge. This flaw exists in the bdecode_recursive function located in include/libtorrent/bencode.hpp of Rasterbar Software libtorrent versions prior to 0.12.1. The vulnerability stems from inadequate input validation and recursive parsing mechanisms that fail to properly handle maliciously crafted bencoded data structures, creating a potential for denial of service attacks that can crash applications and render them unavailable to legitimate users.
The technical exploitation of this vulnerability occurs through the manipulation of bencoded messages, which are the standard encoding format used in bittorrent protocols for transmitting structured data between peers. When the bdecode_recursive function processes a specially crafted bencoded message containing deeply nested structures or circular references, it recursively calls itself without proper depth limits or stack space monitoring. This recursive descent continues until the application exhausts its available stack memory, leading to a stack overflow condition that results in application termination and system instability. The vulnerability is context-dependent because it requires an attacker to have the ability to send malicious bencoded data to the target application, typically through peer-to-peer connections or torrent file manipulation.
From an operational impact perspective, this vulnerability creates significant security risks for applications that rely on libtorrent for peer-to-peer file sharing functionality. The denial of service condition can be exploited by remote attackers to disrupt legitimate file sharing operations, making it particularly dangerous in environments where continuous availability is critical. The vulnerability affects not only Deluge but also numerous other applications that incorporate libtorrent as a core component, including various torrent clients, media streaming applications, and distributed file sharing systems. The impact extends beyond simple service disruption to potentially compromise the reliability of entire peer-to-peer networks that depend on these libraries for their operation.
Security professionals should note that this vulnerability aligns with CWE-674, which describes "Uncontrolled Recursion" as a weakness where recursive functions lack proper termination conditions or depth limits, and it maps to ATT&CK technique T1499.004 for "Endpoint Denial of Service" under the adversary tactics. The recommended mitigation strategy involves upgrading to libtorrent version 0.12.1 or later, where the recursive parsing has been modified to include proper stack depth limitations and input validation. Organizations should also implement network monitoring to detect unusual bencoded message patterns and consider implementing rate limiting for incoming peer connections. Additionally, application-level input sanitization and the use of bounded recursion mechanisms can provide additional defense-in-depth measures against similar vulnerabilities in other software components.