CVE-2026-34792: Endian Firewall RCE Vulnerability

CVE-2026-34792 Overview

CVE-2026-34792 is a command injection vulnerability affecting Endian Firewall version 3.3.25 and prior. Authenticated users can execute arbitrary OS commands via the DATE parameter to /cgi-bin/logs_clamav.cgi. The vulnerability exists because the DATE parameter value is used to construct a file path that is passed to a Perl open() call, which allows command injection due to an incomplete regular expression validation.

Critical Impact

Authenticated attackers can achieve full system compromise by executing arbitrary operating system commands on the firewall appliance, potentially leading to complete network perimeter security bypass.

Affected Products

• Endian Firewall version 3.3.25
• Endian Firewall versions prior to 3.3.25

Discovery Timeline

• 2026-04-02 - CVE-2026-34792 published to NVD
• 2026-04-02 - Last updated in NVD database

Technical Details for CVE-2026-34792

Vulnerability Analysis

This vulnerability is classified as CWE-78 (Improper Neutralization of Special Elements used in an OS Command), commonly known as OS Command Injection. The flaw resides in the ClamAV log viewing functionality of the Endian Firewall web interface.

The vulnerable CGI script /cgi-bin/logs_clamav.cgi accepts a DATE parameter that is intended to specify which log file to display. However, the input validation mechanism uses an incomplete regular expression that fails to properly sanitize all potentially dangerous characters. When this insufficiently validated input is passed to Perl's open() function, attackers can inject shell metacharacters to execute arbitrary commands with the privileges of the web server process.

Since this is a firewall appliance, successful exploitation could allow an attacker to manipulate firewall rules, intercept network traffic, establish persistent backdoor access, or pivot to internal network systems.

Root Cause

The root cause is insufficient input validation of the DATE parameter before it is used in file path construction. The regular expression validation intended to restrict the parameter to safe date formats is incomplete, allowing attackers to bypass the filter and inject command separators and shell metacharacters. When Perl's open() function processes the malicious input, it interprets embedded shell commands due to how Perl handles special characters in file paths.

Attack Vector

The attack is network-based and requires authentication to the Endian Firewall web management interface. An attacker with valid credentials (even low-privilege ones) can craft a malicious HTTP request to the vulnerable CGI endpoint. By manipulating the DATE parameter with shell metacharacters such as pipe characters (|), backticks, or command substitution syntax, the attacker can inject and execute arbitrary OS commands.

The exploitation flow involves:

1. Authenticating to the Endian Firewall web interface
2. Crafting a malicious request to /cgi-bin/logs_clamav.cgi with a manipulated DATE parameter
3. The injected commands execute in the context of the web server process
4. Attacker gains command execution on the firewall appliance

For technical details on the vulnerability mechanism and exploitation, refer to the VulnCheck Advisory on Endian Firewall.

Detection Methods for CVE-2026-34792

Indicators of Compromise

• Unusual HTTP requests to /cgi-bin/logs_clamav.cgi containing shell metacharacters (|, ;, $(), backticks) in the DATE parameter
• Unexpected child processes spawned by the web server process on the Endian Firewall appliance
• Anomalous outbound network connections originating from the firewall management interface
• Modified system files or new user accounts created on the firewall appliance

Detection Strategies

• Implement web application firewall (WAF) rules to detect and block requests containing command injection patterns targeting /cgi-bin/logs_clamav.cgi
• Monitor HTTP access logs for requests to the vulnerable endpoint with unusual DATE parameter values
• Deploy endpoint detection and response (EDR) solutions to monitor for suspicious process execution chains on network appliances
• Enable and review audit logs for authentication events and administrative actions on Endian Firewall devices

Monitoring Recommendations

• Configure SIEM rules to alert on requests to /cgi-bin/logs_clamav.cgi containing special characters or URL-encoded shell metacharacters
• Implement network traffic analysis to detect potential command-and-control communications from firewall appliances
• Regularly audit user accounts with access to the Endian Firewall management interface
• Monitor for file integrity changes on critical system directories of the firewall appliance

How to Mitigate CVE-2026-34792

Immediate Actions Required

• Restrict access to the Endian Firewall web management interface to trusted IP addresses only
• Review and audit all user accounts with access to the firewall management interface, removing unnecessary access
• Implement network segmentation to limit exposure of management interfaces
• Monitor for indicators of compromise and investigate any suspicious activity on affected devices

Patch Information

Consult the Endian Community Help Section for information on available updates and patches. Organizations should upgrade to a patched version as soon as one becomes available from the vendor.

Workarounds

• Restrict management interface access to trusted networks using firewall rules or access control lists
• Implement multi-factor authentication for administrative access where supported
• Consider placing the management interface behind a VPN to reduce attack surface
• Disable or restrict access to the ClamAV logs functionality (/cgi-bin/logs_clamav.cgi) if not operationally required

# Example: Restrict access to management interface using iptables
# Allow management access only from trusted admin network
iptables -A INPUT -p tcp --dport 443 -s 192.168.10.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP