CVE-2023-42000: Arcserve UDP Path Traversal Vulnerability

CVE-2023-42000 Overview

CVE-2023-42000 is a critical path traversal vulnerability affecting Arcserve UDP (Unified Data Protection) prior to version 9.2. The vulnerability exists in the com.ca.arcflash.ui.server.servlet.FileHandlingServlet.doUpload() method, allowing unauthenticated remote attackers to exploit path traversal sequences and upload arbitrary files to any location on the file system where the UDP agent is installed.

Critical Impact

Unauthenticated attackers can upload arbitrary files to any location on the file system, potentially leading to remote code execution, system compromise, and complete loss of data confidentiality, integrity, and availability.

Affected Products

• Arcserve UDP versions prior to 9.2
• Systems running Arcserve UDP agent installations

Discovery Timeline

• 2023-11-27 - CVE-2023-42000 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2023-42000

Vulnerability Analysis

This path traversal vulnerability (CWE-22) resides in the file upload functionality of Arcserve UDP's web interface. The FileHandlingServlet.doUpload() method fails to properly sanitize user-supplied file paths, allowing attackers to escape the intended upload directory and write files to arbitrary locations on the file system.

The vulnerability can be exploited remotely over the network without any authentication requirements, making it particularly dangerous in environments where the Arcserve UDP management interface is exposed. An attacker can leverage this flaw to upload malicious executables, web shells, or configuration files that could lead to complete system compromise.

Root Cause

The root cause is improper input validation in the com.ca.arcflash.ui.server.servlet.FileHandlingServlet.doUpload() method. The servlet fails to sanitize directory traversal sequences (such as ../) from the filename parameter before constructing the destination path. This allows attackers to traverse outside the intended upload directory and place files in arbitrary locations on the target system.

Attack Vector

The attack is network-based and requires no authentication or user interaction. An attacker sends a specially crafted HTTP POST request to the vulnerable servlet endpoint with a filename containing path traversal sequences. The server processes the request and writes the uploaded file content to the attacker-specified location.

For example, an attacker could upload a malicious executable or web shell to a directory that allows code execution, such as the web application's document root or a scheduled task directory. The vulnerability could be chained with other techniques to achieve full remote code execution on the target system.

Technical details and further analysis are available in the Tenable Research Advisory.

Detection Methods for CVE-2023-42000

Indicators of Compromise

• Unusual HTTP POST requests to the FileHandlingServlet endpoint containing ../ or URL-encoded path traversal sequences
• Unexpected files appearing in system directories or outside the normal Arcserve UDP upload paths
• Web shells or suspicious executables discovered in web-accessible directories
• Anomalous file write operations by the Arcserve UDP agent process to non-standard locations

Detection Strategies

• Monitor web application logs for requests containing path traversal patterns targeting Arcserve UDP endpoints
• Implement file integrity monitoring (FIM) on critical system directories to detect unauthorized file uploads
• Deploy network intrusion detection rules to identify path traversal attempts in HTTP traffic
• Review Arcserve UDP access logs for unauthenticated upload requests

Monitoring Recommendations

• Enable detailed logging for the Arcserve UDP web interface and review logs regularly for suspicious activity
• Configure alerts for file creation events in sensitive directories by the Arcserve UDP agent process
• Monitor network traffic to and from Arcserve UDP management ports for unusual patterns
• Implement endpoint detection and response (EDR) solutions to identify post-exploitation activity

How to Mitigate CVE-2023-42000

Immediate Actions Required

• Upgrade Arcserve UDP to version 9.2 or later immediately
• Restrict network access to the Arcserve UDP management interface to trusted IP addresses only
• Place Arcserve UDP management interfaces behind a VPN or firewall that requires authentication
• Review file system for any unauthorized files that may have been uploaded through this vulnerability

Patch Information

Arcserve has addressed this vulnerability in UDP version 9.2. Organizations running affected versions should upgrade to version 9.2 or later as soon as possible. For detailed patch information, consult the Tenable Research Advisory which contains technical details about this vulnerability.

Workarounds

• Implement network-level access controls to restrict access to the Arcserve UDP web interface
• Use a web application firewall (WAF) configured to block path traversal sequences in requests
• If immediate patching is not possible, consider temporarily disabling the web management interface until the upgrade can be performed
• Segment the network to isolate backup infrastructure from general user networks

# Example firewall rule to restrict access to Arcserve UDP web interface (Linux iptables)
# Only allow access from trusted management subnet
iptables -A INPUT -p tcp --dport 8014 -s 10.0.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 8014 -j DROP