CVE-2002-1697 in VTun
Summary
by MITRE
Electronic Code Book (ECB) mode in VTun 2.0 through 2.5 uses a weak encryption algorithm that produces the same ciphertext from the same plaintext blocks, which could allow remote attackers to gain senstive information.
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Analysis
by VulDB Data Team • 06/09/2018
The vulnerability described in CVE-2002-1697 represents a critical cryptographic weakness in the VTun 2.0 through 2.5 network tunneling software that operates at the encryption layer of secure communications. This issue manifests specifically within the Electronic Code Book (ECB) mode implementation, which is a fundamental block cipher encryption mode that processes data in fixed-size blocks without incorporating any form of chaining or initialization vectors. The weakness stems from the deterministic nature of ECB encryption where identical plaintext blocks consistently produce identical ciphertext blocks, creating predictable patterns that can be exploited by adversaries. This vulnerability directly violates the core principles of secure encryption as outlined in industry standards and best practices for cryptographic implementations.
The technical flaw in VTun's implementation of ECB mode creates a significant information disclosure risk that operates at the network protocol level where sensitive data is transmitted through encrypted tunnels. When attackers can observe encrypted network traffic, they can analyze the ciphertext patterns to identify repeated data blocks, potentially reconstructing portions of the original plaintext. This weakness is particularly dangerous because ECB mode does not provide semantic security, meaning that even if an attacker cannot directly read the encrypted data, they can infer information about the underlying communication patterns and content structure. The vulnerability is classified under CWE-327, which specifically addresses the use of weak encryption algorithms and improper cryptographic implementation practices.
The operational impact of this vulnerability extends beyond simple information leakage to potentially enable more sophisticated attacks including traffic analysis, pattern recognition, and partial plaintext reconstruction. Attackers can exploit the deterministic nature of ECB encryption to perform statistical analysis on network traffic, identify communication protocols, and potentially determine the presence of specific data patterns such as headers, footers, or repeated content within the encrypted tunnels. This type of vulnerability aligns with techniques described in the MITRE ATT&CK framework under the Tactic of Credential Access and Defense Evasion, where adversaries can leverage weak encryption to gain insights into network communications and potentially compromise authentication mechanisms that rely on encrypted channels. The vulnerability affects the confidentiality and integrity of data transmitted through VTun tunnels, making it particularly dangerous in environments where sensitive information flows through these encrypted connections.
The remediation approach for this vulnerability requires immediate implementation of stronger encryption modes that incorporate chaining mechanisms and proper initialization vectors to eliminate the deterministic behavior that makes ECB mode susceptible to pattern analysis. Organizations should upgrade from VTun versions 2.0 through 2.5 to patched versions that implement proper encryption modes such as Cipher Block Chaining (CBC) or Counter (CTR) mode, which provide semantic security and prevent the pattern recognition that enables exploitation. Additionally, system administrators should conduct thorough security assessments of all network tunneling implementations to identify similar vulnerabilities in other encryption software and ensure that cryptographic implementations adhere to industry standards such as NIST SP 800-38A for block cipher modes of operation. The vulnerability demonstrates the critical importance of proper cryptographic implementation and the necessity of avoiding deprecated encryption modes that have known weaknesses in modern network security environments.