CVE-2026-34795: Endian Firewall RCE Vulnerability

CVE-2026-34795 Overview

Endian Firewall version 3.3.25 and prior contain a command injection vulnerability that allows authenticated users to execute arbitrary OS commands. The vulnerability exists in the /cgi-bin/logs_log.cgi endpoint, where the DATE parameter value is used to construct a file path that is passed to a Perl open() call. Due to an incomplete regular expression validation, attackers can inject malicious commands that will be executed with the privileges of the web server process.

Critical Impact

Authenticated attackers can achieve full system compromise by executing arbitrary OS commands on affected Endian Firewall appliances, 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 CVE-2026-34795 published to NVD
• 2026-04-02 - Last updated in NVD database

Technical Details for CVE-2026-34795

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 allows authenticated users with access to the firewall's web management interface to escape the intended file path context and inject arbitrary operating system commands.

The attack can be executed remotely over the network and requires low complexity to exploit. An authenticated attacker with basic user privileges can leverage this vulnerability to gain complete control over the firewall appliance, which sits at a critical security boundary in enterprise networks.

Root Cause

The root cause lies in the incomplete input validation of the DATE parameter within the /cgi-bin/logs_log.cgi script. The parameter is intended to specify a date for retrieving log files, but the regular expression used to validate this input fails to account for all possible command injection vectors.

The vulnerability occurs when the DATE parameter value is concatenated into a file path string that is subsequently passed to Perl's open() function. Perl's two-argument open() call has historically been known to interpret certain special characters as pipe operators, allowing command execution when user-controlled input is passed without proper sanitization.

Attack Vector

The attack is network-based, targeting the CGI endpoint at /cgi-bin/logs_log.cgi. An authenticated attacker crafts a malicious request containing specially crafted characters in the DATE parameter. These characters exploit the incomplete regex validation to break out of the file path context and inject shell commands.

When the vulnerable Perl script processes the request, the injected commands are executed with the privileges of the web server process. Given that firewall appliances typically run with elevated privileges, successful exploitation often results in root-level access to the underlying operating system.

The exploitation flow involves sending an HTTP request to the vulnerable CGI script with a payload in the DATE parameter that bypasses the regex filter. The Perl interpreter then executes the injected commands through the open() call, returning command output or establishing a reverse shell to the attacker.

Detection Methods for CVE-2026-34795

Indicators of Compromise

• Unusual HTTP requests to /cgi-bin/logs_log.cgi containing special characters or shell metacharacters in the DATE parameter
• Unexpected processes spawned by the web server process (typically httpd or similar)
• Outbound network connections from the firewall to unknown external IP addresses
• Suspicious entries in web access logs showing encoded pipe characters or command sequences

Detection Strategies

• Monitor web server access logs for requests to /cgi-bin/logs_log.cgi with anomalous DATE parameter values containing pipe (|), backtick (`), or semicolon (;) characters
• Deploy web application firewall (WAF) rules to detect command injection patterns in CGI parameters
• Implement network detection rules to identify reverse shell traffic originating from the firewall appliance
• Enable comprehensive logging on the Endian Firewall and forward logs to a SIEM for anomaly detection

Monitoring Recommendations

• Configure alerts for any child process spawned by the web server that executes shell commands
• Monitor for unauthorized configuration changes or new user accounts on the firewall appliance
• Establish baseline network traffic patterns and alert on deviations, particularly outbound connections to non-standard ports
• Review authentication logs for unusual access patterns to the firewall management interface

How to Mitigate CVE-2026-34795

Immediate Actions Required

• Restrict access to the Endian Firewall web management interface to trusted IP addresses only
• Implement network segmentation to limit the impact of a compromised firewall appliance
• Review and audit all user accounts with access to the firewall management interface
• Monitor the Endian Community Resources for vendor updates and patches

Patch Information

As of the publication date, organizations should consult the VulnCheck Advisory on Endian Firewall for the latest information on available patches and vendor response. Monitor official Endian communications for security updates addressing this command injection vulnerability.

Workarounds

• Restrict management interface access by implementing IP-based access control lists (ACLs) to allow only trusted administrator workstations
• Deploy a reverse proxy with input validation in front of the firewall management interface to filter malicious requests
• Consider temporarily disabling the affected CGI script if log viewing functionality is not critical to operations
• Enable enhanced logging and monitoring while awaiting an official patch from the vendor

# Example: Restrict access to management interface via iptables
# Apply on an upstream firewall or network device
iptables -A INPUT -p tcp --dport 443 -s 10.10.10.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP