CVE-2002-1747 in Vtun
Summary
by MITRE
Vtun 2.5b1 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 ECB.
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Analysis
by VulDB Data Team • 06/09/2018
The vulnerability identified as CVE-2002-1747 affects vtun version 2.5b1, a virtual private network tunneling application that facilitates secure communication over untrusted networks. This flaw represents a critical weakness in the authentication mechanisms implemented within the software, specifically concerning the handling of forwarded packets. The vulnerability stems from the application's failure to properly authenticate packets that are being forwarded through the tunnel, creating a significant security gap that can be exploited by remote attackers.
The technical implementation of this vulnerability lies in the packet forwarding mechanism of vtun where the software does not validate the authenticity of packets before processing them. This lack of authentication allows malicious actors to inject arbitrary data into existing user sessions without triggering any detection mechanisms. The vulnerability is particularly concerning because it operates at the network protocol level, where attackers can manipulate the flow of information between legitimate users and the network infrastructure. The weakness is exacerbated by the fact that the system does not implement proper cryptographic verification of packet integrity, leaving the tunnel susceptible to various forms of injection attacks.
The operational impact of this vulnerability extends beyond simple data injection, as it can potentially enable complete session takeover capabilities. Attackers can leverage cut-and-paste attacks on Electronic Codebook (ECB) mode encryption to manipulate data contents within the tunnel. This cryptographic weakness in ECB mode creates opportunities for attackers to perform replay attacks or modify packet contents in ways that can compromise the integrity of the communication channel. The vulnerability affects the fundamental security assumptions of the tunneling protocol, as it undermines the trust model that users expect when establishing secure connections through vtun.
From a cybersecurity perspective, this vulnerability aligns with CWE-310, which addresses cryptographic issues related to weak encryption modes and improper authentication mechanisms. The attack vector described in CVE-2002-1747 corresponds to techniques documented in the MITRE ATT&CK framework under the T1071.004 sub-technique for application layer protocol manipulation. The lack of packet authentication in vtun creates a persistent threat vector that can be exploited across multiple network sessions, potentially allowing attackers to establish long-term access to network resources. The vulnerability's exploitation requires minimal privileges and can be executed remotely, making it particularly dangerous in enterprise environments where secure communication channels are critical for protecting sensitive data.
The recommended mitigations for this vulnerability include immediate upgrading to a patched version of vtun that implements proper packet authentication mechanisms. Organizations should also consider implementing additional network monitoring solutions to detect anomalous packet patterns that might indicate exploitation attempts. The cryptographic implementation should be reviewed to ensure that ECB mode is not being used for sensitive data encryption, as this mode is inherently weak against pattern analysis attacks. Network segmentation and access control measures can provide additional defense-in-depth layers to limit the potential impact of successful exploitation attempts. Security teams should also implement regular vulnerability assessments to identify similar authentication weaknesses in other network infrastructure components that might be vulnerable to similar attack patterns.