CVE-2026-34790: Endian Firewall Path Traversal Vulnerability

CVE-2026-34790 Overview

CVE-2026-34790 is a directory traversal vulnerability affecting Endian Firewall version 3.3.25 and prior. The vulnerability allows authenticated users to delete arbitrary files on the system by exploiting improper input validation in the remove ARCHIVE parameter of the /cgi-bin/backup.cgi endpoint. The parameter value is used to construct a file path without proper sanitization of directory traversal sequences (e.g., ../), which is then passed directly to an unlink() system call.

Critical Impact
Authenticated attackers can delete critical system files, potentially causing denial of service, disrupting firewall operations, or creating conditions for further exploitation.

Affected Products

Endian Firewall version 3.3.25
Endian Firewall versions prior to 3.3.25

Discovery Timeline

2026-04-02 - CVE-2026-34790 published to NVD
2026-04-02 - Last updated in NVD database

Technical Details for CVE-2026-34790

Vulnerability Analysis

This directory traversal vulnerability (CWE-22) resides in the backup management functionality of Endian Firewall's web interface. The /cgi-bin/backup.cgi script accepts a remove ARCHIVE parameter intended to allow authenticated users to delete backup files. However, the application fails to properly validate or sanitize this input before using it in file system operations.

The vulnerability requires network access and a low-privilege authenticated session to exploit. While confidentiality is not directly impacted, successful exploitation can lead to high integrity impact through unauthorized file deletion and low availability impact due to potential service disruption.

Root Cause

The root cause is improper input validation (CWE-22: Improper Limitation of a Pathname to a Restricted Directory). The remove ARCHIVE parameter value is concatenated into a file path without filtering or validating directory traversal sequences such as ../. This unsanitized path is then passed to the unlink() function, which deletes the file at the specified location regardless of whether it resides within the intended backup directory.

Attack Vector

The attack is network-based and requires authentication. An attacker with valid credentials can craft a malicious HTTP request to the /cgi-bin/backup.cgi endpoint, supplying a remove ARCHIVE parameter containing directory traversal sequences. For example, submitting a value like ../../../etc/passwd would cause the application to attempt deletion of the /etc/passwd file. The attacker can systematically target critical system files, configuration files, or log files to disrupt firewall operations or cover their tracks.

The vulnerability mechanism involves the CGI script accepting user input for the archive filename, constructing a file path by appending this input to a base directory path, and passing the resulting path to unlink() without validation. Technical details are available in the VulnCheck Advisory.

Detection Methods for CVE-2026-34790

Indicators of Compromise

HTTP requests to /cgi-bin/backup.cgi containing ../ sequences in the remove ARCHIVE parameter
Unusual file deletion events in system logs, particularly for files outside the backup directory
Missing critical system configuration files with no administrative explanation
Web server access logs showing repeated requests to the backup.cgi endpoint with suspicious parameter values

Detection Strategies

Implement web application firewall (WAF) rules to detect and block directory traversal patterns in HTTP parameters targeting /cgi-bin/backup.cgi
Configure intrusion detection systems (IDS) to alert on HTTP requests containing path traversal sequences to firewall management interfaces
Enable and monitor file integrity monitoring (FIM) for critical system files and directories
Review web server access logs for anomalous patterns involving the backup management endpoint

Monitoring Recommendations

Enable verbose logging for the Endian Firewall web management interface
Monitor file system audit logs for unexpected unlink() operations on system-critical paths
Set up alerts for authentication events followed by suspicious backup.cgi access patterns
Implement centralized log collection to detect potential exploitation attempts across multiple devices

How to Mitigate CVE-2026-34790

Immediate Actions Required

Restrict access to the Endian Firewall web management interface to trusted networks and administrators only
Review access logs for any indicators of exploitation attempts
Implement network segmentation to limit exposure of firewall management interfaces
Consider temporarily disabling the backup functionality if not operationally required until a patch is available

Patch Information

No vendor patch information is currently available in the CVE data. Administrators should monitor the Endian Community Help Section for security updates and patch announcements. Contact Endian support for guidance on remediation options.

Workarounds

Implement strict network access controls (ACLs) to limit which IP addresses can reach the /cgi-bin/backup.cgi endpoint
Deploy a web application firewall (WAF) with rules to block requests containing directory traversal patterns
Restrict backup management functionality to specific administrative accounts with enhanced monitoring
Consider placing the firewall management interface on an isolated management VLAN

bash

# Example: Restrict access to management interface via iptables
# Allow only trusted management network
iptables -A INPUT -p tcp --dport 443 -s 10.0.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP