CVE-2021-47667
Vulnerability: OS Command Injection in ZendTo
Description:
Unauthenticated remote attackers can execute arbitrary operating system commands due to insufficient input sanitization in the tmp_name parameter when processing file drop-off requests. Specifically, shell metacharacters are not properly escaped or filtered within the lib/NSSDropoff.php script when handling a POST request to the /dropoff endpoint.
Severity:
Critical (CVSS v3 score of 10.0) due to the potential for unauthenticated remote code execution.
Known Exploit:
An attacker can craft a malicious POST request to the /dropoff endpoint, including shell metacharacters (e.g., ;, |, &&) within the tmp_name parameter. When the ZendTo application processes this request, it will execute the embedded commands on the server with the privileges of the web server user. This allows the attacker to potentially gain control of the server, read sensitive data, or launch further attacks.
Remediation / Mitigation Strategy:
Upgrade ZendTo: The primary solution is to upgrade to ZendTo version 6.10-7 or later. These versions contain the necessary fixes to properly sanitize the
tmp_nameparameter.Input Sanitization: If upgrading is not immediately possible, implement strict input validation and sanitization on the
tmp_nameparameter inlib/NSSDropoff.php. Specifically:- Whitelist Approved Characters: Only allow alphanumeric characters, underscores, periods, and hyphens in the
tmp_namevalue. Reject any requests containing shell metacharacters. - Escape Shell Metacharacters: If you must allow a broader range of characters, properly escape all shell metacharacters before passing the
tmp_namevalue to any shell commands. Use functions appropriate for your operating system (e.g.,escapeshellarg()in PHP).
- Whitelist Approved Characters: Only allow alphanumeric characters, underscores, periods, and hyphens in the
Web Application Firewall (WAF): Deploy a web application firewall (WAF) with rules that can detect and block requests containing shell metacharacters in the
tmp_nameparameter of POST requests to the/dropoffendpoint. This provides an additional layer of protection even if the application-level fix is not yet fully deployed.Network Segmentation: Isolate the ZendTo server within a segmented network to limit the potential damage if an attacker successfully exploits the vulnerability. Ensure that the server has only the necessary network access to perform its intended functions.
Monitor Logs: Continuously monitor web server logs and intrusion detection system (IDS) alerts for suspicious activity related to the
/dropoffendpoint, such as failed login attempts, unusual URL parameters, or attempts to execute shell commands.Regular Security Audits: Conduct regular security audits and penetration testing to identify and address any potential vulnerabilities in the ZendTo application and its infrastructure.
Principle of Least Privilege: Ensure that the web server user has only the minimal necessary privileges. This limits the potential impact if an attacker gains control of the server.
Assigner
- MITRE [email protected]
Date
- Published Date: 2025-04-05 00:00:00
- Updated Date: 2025-04-05 05:11:43