CVE-2017-17715 in Telegram Messenger
Summary
by MITRE
The saveFile method in MediaController.java in the Telegram Messenger application before 2017-12-08 for Android allows directory traversal via a pathname obtained in a file-transfer request from a remote peer, as demonstrated by writing to tgnet.dat or tgnet.dat.bak.
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Analysis
by VulDB Data Team • 12/15/2019
The vulnerability identified as CVE-2017-17715 represents a critical directory traversal flaw within the Telegram Messenger Android application that existed prior to the December 8, 2017 release. This security weakness resides in the MediaController.java component and specifically affects the saveFile method which handles file transfer operations from remote peers. The vulnerability stems from inadequate input validation and sanitization of file paths received during file transfer requests, creating an exploitable condition that allows remote attackers to manipulate the destination path of saved files.
The technical implementation of this vulnerability enables attackers to craft malicious file transfer requests that can bypass normal file system access controls and write files to arbitrary locations within the application's directory structure. The demonstration of this flaw shows successful exploitation targeting critical system files such as tgnet.dat and tgnet.dat.bak, which are essential components of Telegram's network communication infrastructure. These files contain network-related data and configuration information that when modified or overwritten can significantly impact the application's functionality and security posture.
The operational impact of this vulnerability extends beyond simple unauthorized file creation as it provides attackers with the capability to modify critical application files that could lead to persistent access, data corruption, or even complete application compromise. When combined with other attack vectors, this directory traversal vulnerability could enable adversaries to inject malicious code into the application's network components, potentially allowing for man-in-the-middle attacks or data exfiltration. The vulnerability affects the integrity and confidentiality of user communications by compromising the underlying file system operations that support secure messaging functionality.
This vulnerability maps to CWE-22 - Improper Limitation of a Pathname to a Restricted Directory and aligns with ATT&CK technique T1059.007 - Command and Scripting Interpreter: PowerShell, though the exploitation occurs at the file system level rather than through scripting. The weakness represents a classic path traversal vulnerability that demonstrates poor input validation practices in mobile application development, particularly in the handling of user-supplied data in file system operations. The flaw indicates inadequate sandboxing and access control mechanisms within the Telegram Android application's file handling procedures, creating a persistent security risk for all users of vulnerable versions.
Mitigation strategies should include immediate deployment of the patched Telegram application version released on December 8, 2017, which addresses the directory traversal vulnerability through proper input validation and path sanitization. Organizations should implement network monitoring to detect anomalous file transfer patterns that could indicate exploitation attempts, while also ensuring proper application sandboxing and file system access controls are maintained. Additionally, users should be educated about the importance of keeping messaging applications updated and should avoid accepting file transfers from untrusted sources. The vulnerability highlights the critical need for mobile application developers to implement robust input validation and access control measures, particularly when handling file operations that involve user-provided data from remote sources.