Overview
The Common Vulnerabilities and Exposures (CVE) system has identified a critical security flaw in certain TOTOLink routers, referenced as CVE-2025-44655. This vulnerability arises due to an insecure configuration setting in the vsftpd.conf file. As it stands, organizations and individuals using the affected routers are at a significant risk of unauthorized access to system files, privilege escalation, or the use of the compromised server as a pivot point for internal network attacks. This blog post delves into the specifics of CVE-2025-44655, its potential impacts, and how affected users can mitigate these risks.
Vulnerability Summary
CVE ID: CVE-2025-44655
Severity: Critical (9.8)
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: Unauthorized access to system files, privilege escalation, potential system compromise or data leakage
Affected Products
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Product | Affected Versions
TOTOLink A7100RU | V7.4
TOTOLink A950RG | V5.9
TOTOLink T10 | V5.9
How the Exploit Works
The exploitation of this vulnerability is rooted in the enabled “chroot_local_user” option in the “vsftpd.conf” file. When enabled, this option allows for an unauthorized FTP client to access the root directory of the server. An attacker can leverage this configuration flaw to gain unauthorized access to system files or escalate privileges. Furthermore, a compromised server can be used as a launchpad for additional internal network attacks.
Conceptual Example Code
Here is a conceptual example of how an attacker might exploit the vulnerability using an FTP client:
ftp> open target.example.com
Connected to target.example.com.
220 Welcome to TOTOLink FTP service.
Name (target.example.com:attacker): anonymous
331 Please specify the password.
Password:
230 Login successful.
Remote system type is UNIX.
Using binary mode to transfer files.
ftp> cd ..
250 Directory successfully changed.
ftp> get vsftpd.conf
200 PORT command successful. Consider using PASV.
150 Opening BINARY mode data connection for vsftpd.conf (1234 bytes).
226 Transfer complete.
ftp> quit
221 Goodbye.In this example, the attacker is able to log in as an anonymous user and navigate to the root directory to obtain the “vsftpd.conf” file. This file can then be analyzed to gain valuable information about the server’s configuration and potentially exploit further vulnerabilities.
Mitigation Guidance
The primary mitigation strategy for this vulnerability is to apply the vendor’s patch as soon as it becomes available. In the interim, organizations are advised to employ a Web Application Firewall (WAF) or an Intrusion Detection System (IDS) as temporary mitigation measures against potential exploits. Additionally, organizations can manually disable the “chroot_local_user” option in the “vsftpd.conf” file to prevent unauthorized access to the root directory. It is crucial to remember to monitor system logs to detect any suspicious activity continually.