CVE-2006-6719 in wget
Summary
by MITRE
The ftp_syst function in ftp-basic.c in Free Software Foundation (FSF) GNU wget 1.10.2 allows remote attackers to cause a denial of service (application crash) via a malicious FTP server with a large number of blank 220 responses to the SYST command.
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Analysis
by VulDB Data Team • 06/14/2025
The vulnerability described in CVE-2006-6719 represents a classic buffer overflow scenario within the GNU wget application that specifically targets the ftp_syst function in the ftp-basic.c source file. This flaw exists in version 1.10.2 of the widely used command-line utility for retrieving files from the web using http and ftp protocols. The issue manifests when wget attempts to process responses from an FTP server during the SYST command execution, which is used to determine the type of operating system on the remote server. The vulnerability stems from inadequate input validation and buffer management within the ftp_syst function, creating a condition where the application fails to properly handle malformed or excessively long responses from the FTP server. This particular weakness allows remote attackers to craft malicious FTP server responses that contain a large number of blank lines in the 220 response, which is the standard response code indicating that the server is ready for the connection.
The technical exploitation of this vulnerability occurs when the ftp_syst function processes the malformed 220 response from a malicious FTP server. The function fails to properly sanitize or limit the number of blank lines in the response, causing an integer overflow or buffer over-read condition that ultimately leads to application crash. The flaw operates at the protocol level where wget expects a standard response format but receives an unexpected sequence of blank lines that cause memory corruption. This type of vulnerability falls under the CWE-121 category of stack-based buffer overflow, though it could also be classified as CWE-787 out-of-bounds write depending on the specific implementation details of how the buffer is managed during response parsing. The vulnerability is particularly dangerous because it requires no authentication or special privileges from the attacker, making it a remote code execution or denial of service vector that can be exploited over the network.
From an operational impact perspective, this vulnerability creates a significant risk for any system running GNU wget 1.10.2 that connects to untrusted FTP servers. The denial of service condition means that legitimate users cannot utilize wget for downloading files from FTP servers, effectively disrupting automated download processes, web scraping activities, and system administration tasks that rely on this utility. The vulnerability is especially concerning in environments where wget is used for automated tasks such as software updates, backup operations, or content synchronization, as a single malicious FTP server could compromise entire automated workflows. The attack vector is straightforward and requires minimal technical expertise, making it particularly dangerous in production environments where wget is frequently used to access external resources. This vulnerability also represents a potential gateway for more sophisticated attacks if attackers can leverage the denial of service to disrupt critical services or create conditions for additional exploitation attempts.
The recommended mitigations for CVE-2006-6719 involve immediate patching of GNU wget to version 1.11 or later, where the ftp_syst function has been properly modified to handle malformed responses and implement proper bounds checking. System administrators should also implement network-level controls to restrict access to known malicious FTP servers and consider implementing proxy configurations that can filter or sanitize FTP responses before they reach the wget client. Additionally, organizations should conduct regular vulnerability assessments to identify other instances of older wget versions in their environments and ensure proper patch management procedures are in place. The ATT&CK framework categorizes this vulnerability under the T1190 - Exploit Public-Facing Application technique, as it represents an exploitation of a publicly accessible network service through a flaw in a widely used application. Organizations should also consider implementing network segmentation and monitoring to detect unusual FTP traffic patterns that might indicate exploitation attempts. The vulnerability underscores the importance of proper input validation and defensive programming practices in network applications, particularly those that handle user-provided data from untrusted sources.