CVE-2018-17613 in Telegram
Summary
by MITRE
Telegram Desktop (aka tdesktop) 1.3.16 alpha, when "Use proxy" is enabled, sends credentials and application data in cleartext over the SOCKS5 protocol.
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Analysis
by VulDB Data Team • 03/28/2020
The vulnerability identified as CVE-2018-17613 affects Telegram Desktop version 1.3.16 alpha and represents a critical security flaw in the application's proxy handling mechanism. This issue specifically manifests when users enable the "Use proxy" functionality within the application, creating a scenario where sensitive information flows through the SOCKS5 protocol without proper encryption. The flaw stems from the application's failure to implement secure communication channels when routing traffic through proxy servers, leaving user credentials and application data exposed to potential interception.
The technical implementation of this vulnerability involves the Telegram Desktop client's improper handling of SOCKS5 proxy connections where cleartext transmission occurs during the authentication and data transfer phases. When users configure proxy settings, the application establishes connections using SOCKS5 protocol but fails to negotiate or implement encryption mechanisms that would normally be expected in secure proxy communications. This creates a man-in-the-middle attack surface where network traffic containing user credentials, chat messages, and other sensitive application data can be captured and read by malicious actors monitoring the network traffic.
The operational impact of this vulnerability extends beyond simple credential exposure to encompass comprehensive data leakage from the application. Attackers who can intercept network traffic between the Telegram Desktop client and proxy servers gain access to plaintext user credentials, message content, and potentially other application-specific data that flows through the proxy connection. This vulnerability directly violates the principle of least privilege and secure communication practices, as the application fails to maintain confidentiality of user data even when operating in supposedly secure environments. The flaw particularly affects users who rely on proxy servers for network access, which is common in corporate environments, educational institutions, or regions with restricted internet access.
From a cybersecurity perspective, this vulnerability aligns with CWE-312 (Cleartext Storage of Sensitive Information) and CWE-319 (Cleartext Transmission of Sensitive Information), as it involves the transmission of sensitive data in an unencrypted format over network connections. The issue also maps to ATT&CK technique T1041 (Exfiltration Over C2 Channel) and T1071.004 (Application Layer Protocol: DNS) when considering the broader attack surface. Organizations using Telegram Desktop in environments where proxy servers are required should immediately assess their network security posture, as this vulnerability could be exploited to compromise user accounts and access sensitive communications. The remediation requires immediate patching of the application to implement proper encryption mechanisms when establishing SOCKS5 proxy connections, ensuring that all authentication credentials and data are transmitted through secure channels that comply with industry standards for secure communications.
The vulnerability demonstrates a critical gap in secure coding practices and network security implementation within the Telegram Desktop application. Security professionals should note that this flaw represents a failure in proper protocol implementation where the application does not adhere to established security best practices for proxy connectivity. Network administrators and security teams must consider this vulnerability when evaluating the security posture of applications that route traffic through proxy servers, as it highlights the importance of implementing proper encryption requirements even for applications that appear to function correctly under normal circumstances. The issue underscores the necessity of comprehensive security testing that includes network protocol analysis and traffic inspection to identify potential cleartext data transmission vulnerabilities in client applications.