CVE-2002-0872 in l2tpd
Summary
by MITRE
l2tpd 0.67 does not initialize the random number generator, which allows remote attackers to hijack sessions.
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Analysis
by VulDB Data Team • 05/11/2019
The vulnerability identified as CVE-2002-0872 affects l2tpd version 0.67, a Layer 2 Tunneling Protocol daemon commonly used for establishing L2TP connections in virtual private network implementations. This flaw represents a critical security weakness that undermines the integrity of session management within the protocol stack. The vulnerability stems from improper initialization of the random number generator during the daemon's startup sequence, creating predictable cryptographic values that can be exploited by malicious actors. The impact extends beyond simple session hijacking to potentially compromise entire network communications and user data confidentiality.
The technical root cause of this vulnerability lies in the insufficient seeding of the random number generator used by l2tpd during session establishment. When a daemon fails to properly initialize its random number generator, it produces predictable sequence values that adversaries can reverse engineer or guess. This weakness specifically affects the generation of session identifiers, tunnel identifiers, and other cryptographic parameters that should remain unpredictable to maintain security. According to CWE-330, this represents an inadequate entropy source that leads to predictable random number generation, making the system susceptible to various attack vectors including session prediction and hijacking.
The operational impact of CVE-2002-0872 allows remote attackers to establish unauthorized connections and take control of existing L2TP sessions without proper authentication. Attackers can leverage the predictable random values to guess session parameters and inject malicious traffic into active connections, potentially leading to data interception, modification, or complete session takeover. This vulnerability particularly affects networks relying on L2TP for secure remote access, VPN implementations, and enterprise network connections where session integrity is paramount. The attack surface is broad as any system running vulnerable l2tpd versions becomes susceptible to exploitation, regardless of network segmentation or other security controls.
Mitigation strategies for this vulnerability require immediate patching of affected l2tpd installations to version 0.68 or later, which properly initializes the random number generator. System administrators should also implement additional network security measures such as IPsec encryption for L2TP connections to provide cryptographic protection even when session identifiers are predictable. The ATT&CK framework categorizes this vulnerability under T1071.004 for application layer protocol usage and T1566 for credential harvesting through session hijacking techniques. Organizations should conduct comprehensive vulnerability assessments to identify all systems running affected l2tpd versions and implement network monitoring to detect potential exploitation attempts. Additional defensive measures include configuring firewalls to restrict L2TP traffic to trusted sources and implementing intrusion detection systems to monitor for suspicious session establishment patterns.