A significant security flaw has been identified in ZendTo, a widely used web-based file transfer application. This vulnerability, designated as CVE-2025-34508, allows authenticated users to exploit path traversal techniques to access sensitive files on the host system. The affected versions range from 6.15 to 7 and earlier, highlighting the ongoing risks associated with web-based file transfer solutions.
Understanding the Vulnerability
ZendTo is a PHP-based platform that facilitates secure file sharing by enabling registered users to upload and download files. During the file upload process, two variables—`chunkName` and `tmp_name`—are utilized to manage how files are staged and moved within the system.
Security researchers at Horizon3.ai have discovered that the server-side sanitization routine in ZendTo strips non-alphanumeric characters from `chunkName`. However, if an attacker supplies a `chunkName` composed entirely of non-alphanumeric characters, the sanitization process results in an empty or dot-only string. This leads to the `chunkPath` pointing to the root uploads directory instead of a unique temporary file.
Once the `chunkPath` is established, the code concatenates a user-controlled `tmp_name` to relocate the file into the target dropoff directory. Since `tmp_name` is not sanitized, attackers can embed directory traversal sequences. By downloading this file, the application’s log data, including dropoff claim IDs, can be exposed. This creates a pathway for attackers to enumerate and exfiltrate user-uploaded content or critical system files.
Risk Factors and Impact
The primary risk factors associated with CVE-2025-34508 include:
– Affected Products: ZendTo versions 6.15–7 and prior.
– Impact: Arbitrary file read and information disclosure.
– Exploit Prerequisites: Low-privilege authenticated user.
– CVSS 3.1 Score: 7.8 (High).
In default installations, file access is limited to the `www-root` user’s permissions. However, this typically encompasses all uploaded content. Beyond user files, adversaries could target the ZendTo database or source code, potentially causing a denial-of-service. Although CVE-2025-34508 requires authentication, the minimal barrier allows low-privilege users to perform arbitrary file reads.
Mitigation Measures
Administrators are strongly urged to upgrade immediately. The fix implements stricter validation on both `chunkName` and `tmp_name`, ensuring only safe, expected filenames are processed. This disclosure follows high-profile incidents involving MOVEit Transfer (CVE-2023-34362), Accellion FTA (CVE-2021-27104), and GoAnywhere MFT (CVE-2023-0669), highlighting that file-sharing platforms remain prime targets. Organizations must maintain vigilant patch management and conduct regular security reviews of their file transfer applications.
Broader Implications
This vulnerability underscores the persistent risks in web-based file transfer applications. Similar vulnerabilities have been exploited in other platforms, leading to significant data breaches and operational disruptions. For instance, the MOVEit Transfer vulnerability (CVE-2023-34362) allowed attackers to execute arbitrary code, leading to unauthorized access to sensitive data. Similarly, the Accellion FTA vulnerability (CVE-2021-27104) was exploited to steal data from numerous organizations, resulting in substantial financial and reputational damage.
The exploitation of such vulnerabilities often follows a pattern:
1. Discovery: Attackers identify a flaw in the application, such as improper input validation or inadequate sanitization processes.
2. Exploitation: By crafting specific inputs, attackers can manipulate the application to access unauthorized data or execute arbitrary code.
3. Data Exfiltration: Once access is gained, sensitive data can be extracted, leading to potential data breaches.
4. Operational Disruption: In some cases, attackers may deploy ransomware or other malicious payloads, causing significant operational disruptions.
Preventive Strategies
To mitigate the risks associated with such vulnerabilities, organizations should adopt a multi-faceted approach:
– Regular Updates: Ensure that all software, especially web-based applications, are updated promptly to incorporate security patches.
– Input Validation: Implement robust input validation mechanisms to prevent malicious inputs from being processed.
– Access Controls: Restrict access to sensitive files and directories, ensuring that only authorized users have the necessary permissions.
– Monitoring and Logging: Continuously monitor system logs for unusual activities and set up alerts for potential security incidents.
– User Education: Educate users about the importance of security practices, such as using strong passwords and recognizing phishing attempts.
Conclusion
The discovery of CVE-2025-34508 in ZendTo serves as a stark reminder of the vulnerabilities inherent in web-based file transfer applications. Organizations must remain vigilant, ensuring that they implement robust security measures and stay informed about potential threats. By adopting a proactive approach to cybersecurity, organizations can protect their sensitive data and maintain the trust of their stakeholders.
