CVE-2017-7183 in ExtraPuTTY
Summary
by MITRE
The TFTP server in ExtraPuTTY 0.30 and earlier allows remote attackers to cause a denial of service (crash) via a large (1) read or (2) write TFTP protocol message.
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Analysis
by VulDB Data Team • 12/10/2025
The vulnerability identified as CVE-2017-7183 affects the TFTP server component within ExtraPuTTY version 0.30 and earlier releases, representing a critical denial of service weakness that can be exploited by remote attackers to crash the affected system. This flaw specifically targets the TFTP protocol implementation within the ExtraPuTTY application, which is a graphical user interface for the PuTTY SSH and telnet client that includes additional features for network administration and troubleshooting. The vulnerability manifests when the TFTP server receives malformed or excessively large read or write requests, causing the application to crash and become unavailable to legitimate users.
The technical flaw stems from inadequate input validation and buffer management within the TFTP server implementation. When processing TFTP read (RRQ) or write (WRQ) requests, the system fails to properly validate the size and structure of incoming packets, allowing attackers to craft specially crafted messages that exceed the expected buffer limits. This lack of proper boundary checking creates a condition where the application attempts to process data that exceeds allocated memory space, leading to memory corruption and subsequent application termination. The vulnerability is classified under CWE-121 as a stack-based buffer overflow condition, where insufficient validation of input parameters results in memory corruption that can be exploited to cause system instability.
From an operational perspective, this vulnerability presents significant risk to network infrastructure administrators who rely on ExtraPuTTY for network device management and configuration tasks. The denial of service impact means that legitimate users attempting to perform TFTP operations such as firmware upgrades, configuration file transfers, or network device diagnostics will be unable to complete these operations when the server crashes. This disruption can cascade into broader network management issues, particularly in environments where automated processes depend on TFTP functionality for routine maintenance tasks. The remote exploitation aspect means that attackers do not need physical access or local network privileges to trigger the vulnerability, making it particularly dangerous in publicly accessible network environments.
The attack vector for this vulnerability aligns with ATT&CK technique T1499.004, which involves network disruption through denial of service attacks. Attackers can leverage this weakness by simply sending a specially crafted TFTP read or write request to the vulnerable server, making the exploitation relatively simple and requiring minimal technical expertise. The vulnerability affects the availability aspect of the CIA triad, as it prevents legitimate users from accessing the TFTP service. Organizations using ExtraPuTTY versions prior to 0.31 should consider this vulnerability as a high-priority issue requiring immediate attention, particularly in environments where network management services are critical to business operations. The impact extends beyond simple service interruption to potentially disrupting automated network management workflows and configuration management processes that depend on reliable TFTP functionality.
Mitigation strategies should include immediate patching to version 0.31 or later of ExtraPuTTY, which contains the necessary fixes for input validation and buffer management. Network administrators should also implement network segmentation and access controls to limit exposure of vulnerable TFTP servers to untrusted networks. Additionally, monitoring systems should be configured to detect unusual TFTP traffic patterns that might indicate exploitation attempts. The vulnerability demonstrates the importance of proper input validation and memory management in network services, highlighting that even seemingly simple protocols like TFTP can present significant security risks when not properly implemented. Organizations should also consider implementing network-based intrusion detection systems to monitor for suspicious TFTP activity and establish incident response procedures for handling potential exploitation attempts.