CVE-2002-1755 in tinc
Summary
by MITRE
tinc 1.0pre3 and 1.0pre4 VPN does not authenticate forwarded packets, which allows remote attackers to inject data into user sessions without detection, and possibly control the data contents via cut-and-paste attacks on CBC.
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Analysis
by VulDB Data Team • 06/09/2018
The vulnerability described in CVE-2002-1755 affects the tinc VPN software version 1.0pre3 and 1.0pre4, representing a critical security flaw in the authentication mechanisms of the network communication protocol. This issue stems from the software's failure to properly authenticate forwarded packets, creating a significant weakness in the security architecture that enables malicious actors to exploit the system without detection. The vulnerability specifically targets the integrity and authenticity guarantees that should be maintained throughout the VPN communication channels, fundamentally undermining the trust model that users expect from secure network connections.
The technical implementation of this flaw involves the absence of proper packet authentication mechanisms within the tinc VPN framework, particularly when handling forwarded network traffic. When packets are transmitted through the VPN infrastructure, the system fails to validate their authenticity before forwarding them to their intended destinations. This weakness allows attackers to inject malicious data into existing user sessions by crafting specially formatted packets that appear legitimate to the receiving system. The vulnerability is particularly concerning because it enables what is known as a cut-and-paste attack, where an attacker can manipulate data flows by intercepting and reinserting packets at strategic points within the network communication path, effectively bypassing the normal authentication procedures that should protect against such interference.
The operational impact of this vulnerability extends beyond simple data injection attacks to potentially enable complete control over data contents within the VPN sessions. Attackers can leverage this weakness to modify or replace legitimate data with malicious content, creating a scenario where the integrity of communications is compromised. The CBC (Cipher Block Chaining) vulnerability mentioned in the description indicates that the attack can be particularly effective against encryption modes that rely on chained block operations, where modifications to one block can influence subsequent blocks in the cipher stream. This type of attack pattern aligns with common tactics used in network protocol manipulation and can be categorized under attack techniques that compromise data integrity and authenticity.
From a cybersecurity perspective, this vulnerability represents a failure in the fundamental security principles of authentication and data integrity protection, which are core components of the CIA triad. The weakness can be mapped to CWE-310, which addresses cryptographic issues related to authentication failures, and connects to broader ATT&CK framework concepts involving network infiltration and data manipulation techniques. The vulnerability demonstrates how incomplete implementation of security controls can create exploitable gaps in even well-intentioned security systems, particularly when dealing with network protocols that must maintain trust between communicating parties. Organizations using affected versions of tinc VPN software face significant risk of undetected data compromise and potential unauthorized access to their network communications, making this vulnerability particularly dangerous in environments where sensitive information flows through the VPN infrastructure.
The recommended mitigation strategies include immediate upgrade to patched versions of the tinc software where authentication mechanisms have been properly implemented and tested. System administrators should also implement additional network monitoring and intrusion detection measures to identify potential exploitation attempts, while considering network segmentation and access controls to limit the potential impact of successful attacks. Organizations should conduct thorough security assessments of their VPN configurations and ensure that all network traffic is properly authenticated and encrypted, with particular attention to the implementation of secure cryptographic protocols that prevent the types of cut-and-paste attacks that exploit this vulnerability.