CVE-2005-2779 in iTAN Online-Banking Security System
Summary
by MITRE
The iTAN Online-Banking Security System allows remote attackers to obtain TAN numbers via a man-in-the-middle (MITM) attack while the transaction is taking place, which facilitates a "phishing" attack.
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Analysis
by VulDB Data Team • 07/26/2017
The iTAN Online-Banking Security System vulnerability represents a critical weakness in financial transaction security protocols that enables remote attackers to intercept sensitive authentication numbers during online banking operations. This vulnerability specifically targets the communication channel between banking clients and servers, creating an exploitable condition that undermines the fundamental security assumptions of the system. The flaw operates by allowing adversaries to position themselves between legitimate banking participants and the financial institution's servers, effectively creating a transparent proxy that can observe and potentially manipulate transaction data in real-time. This type of attack vector directly violates the principle of secure communication channels that financial institutions must maintain to protect customer transactions.
The technical implementation of this vulnerability stems from inadequate cryptographic protection mechanisms and insufficient authentication verification during the transaction process. Attackers can exploit this weakness through various man-in-the-middle techniques that do not require sophisticated tools or deep system knowledge, making the attack surface particularly concerning for widespread exploitation. The vulnerability specifically affects the TAN (Transaction Authentication Number) generation and transmission process, where these authentication numbers are susceptible to interception while traveling through potentially unencrypted or weakly encrypted communication pathways. This flaw aligns with CWE-310, which categorizes cryptographic weaknesses and the absence of proper encryption mechanisms as critical security vulnerabilities. The system's failure to implement robust end-to-end encryption or proper certificate validation creates an environment where attackers can seamlessly insert themselves into the communication flow without detection.
The operational impact of this vulnerability extends beyond simple information disclosure to encompass full transaction compromise and potential financial fraud. When attackers successfully intercept TAN numbers, they gain the capability to execute unauthorized transactions on behalf of legitimate users, effectively bypassing the security controls that should protect against such unauthorized access. This vulnerability enables sophisticated phishing operations where attackers can collect authentication data and immediately use it to complete fraudulent transactions without requiring additional user interaction or knowledge of the victim's credentials. The attack methodology directly corresponds to the ATT&CK technique T1566, which describes social engineering attacks that manipulate individuals into divulging confidential information or performing actions that compromise security. The vulnerability's exploitation can result in significant financial losses for both individual users and financial institutions, while also undermining public confidence in online banking security measures.
Mitigation strategies for this vulnerability must address both immediate protective measures and long-term architectural improvements to prevent similar weaknesses in the system design. Organizations should implement robust end-to-end encryption protocols using industry-standard cryptographic algorithms such as TLS 1.3 with strong cipher suites to prevent interception of transaction data. The system must enforce strict certificate validation procedures and implement proper certificate pinning mechanisms to prevent man-in-the-middle attacks from succeeding. Additionally, financial institutions should deploy network monitoring tools to detect anomalous communication patterns that may indicate active interception attempts. Security controls should include transaction integrity checks, real-time fraud detection systems, and multi-factor authentication mechanisms that provide additional layers of protection beyond simple TAN numbers. The implementation of these measures aligns with NIST cybersecurity framework recommendations for protecting financial transaction systems and addresses the fundamental security gaps that allowed this vulnerability to exist and be successfully exploited by remote attackers.