CVE-2026-34797: Endian Firewall RCE Vulnerability

CVE-2026-34797 Overview

CVE-2026-34797 is a command injection vulnerability affecting Endian Firewall version 3.3.25 and prior. The vulnerability exists in the /cgi-bin/logs_smtp.cgi endpoint, where the DATE parameter value is used to construct a file path that is passed to a Perl open() call. Due to incomplete regular expression validation, authenticated users can inject arbitrary OS commands through the DATE parameter, leading to full system compromise.

Critical Impact

Authenticated attackers can execute arbitrary operating system commands on the Endian Firewall appliance, potentially leading to complete system compromise, data exfiltration, and lateral movement within the network.

Affected Products

• Endian Firewall version 3.3.25
• Endian Firewall versions prior to 3.3.25
• Endian Firewall Community Edition (affected versions)

Discovery Timeline

• 2026-04-02 - CVE-2026-34797 published to NVD
• 2026-04-02 - Last updated in NVD database

Technical Details for CVE-2026-34797

Vulnerability Analysis

This command injection vulnerability (CWE-78) affects the SMTP log viewing functionality in Endian Firewall. The vulnerable endpoint /cgi-bin/logs_smtp.cgi accepts a DATE parameter that is intended to specify which log file to display. However, the input validation mechanism relies on an incomplete regular expression that fails to properly sanitize special characters used in Perl command injection.

When the DATE parameter is processed, the value is concatenated into a file path string that gets passed to Perl's open() function. Perl's open() call has a well-documented security concern where certain special characters (such as pipe characters |) can be used to execute shell commands instead of opening files. The incomplete regex validation allows attackers to bypass the intended restrictions and inject malicious commands.

Since this vulnerability requires authentication, it represents a post-authentication attack vector. However, once an attacker has valid credentials (which could be obtained through credential stuffing, phishing, or default credentials), they can achieve complete control over the firewall appliance with the privileges of the web server process.

Root Cause

The root cause of this vulnerability is insufficient input validation on the DATE parameter in the /cgi-bin/logs_smtp.cgi script. The regular expression used to validate the parameter does not account for all possible command injection payloads that can be processed by Perl's open() function. Specifically, the validation fails to properly sanitize pipe characters and other shell metacharacters that enable command execution through Perl's two-argument form of open().

Attack Vector

The attack vector is network-based and requires authentication. An attacker with valid credentials to the Endian Firewall web interface can exploit this vulnerability by sending a crafted HTTP request to the /cgi-bin/logs_smtp.cgi endpoint with a malicious DATE parameter.

The attack leverages Perl's open() function behavior where a filename starting or ending with a pipe character (|) causes the remainder of the string to be executed as a shell command. By crafting a DATE parameter that bypasses the incomplete regex validation while still containing command injection syntax, the attacker can execute arbitrary commands on the underlying operating system.

For example, an attacker might craft a request where the DATE parameter contains shell commands that will be executed when Perl processes the malicious input through the open() call. The commands execute with the privileges of the web server process, which on firewall appliances often has elevated privileges.

For detailed technical information and proof-of-concept details, refer to the VulnCheck Advisory on Command Injection.

Detection Methods for CVE-2026-34797

Indicators of Compromise

• Unusual HTTP requests to /cgi-bin/logs_smtp.cgi containing pipe characters (|) or shell metacharacters in the DATE parameter
• Unexpected process spawning from the web server process on the Endian Firewall appliance
• Anomalous outbound network connections originating from the firewall appliance
• Suspicious entries in web server access logs showing encoded or obfuscated DATE parameter values

Detection Strategies

• Implement web application firewall (WAF) rules to detect and block requests containing shell metacharacters in the DATE parameter
• Monitor authentication logs for unusual login patterns that may indicate credential compromise
• Deploy network intrusion detection systems (NIDS) with signatures for Perl command injection patterns
• Enable detailed logging on the Endian Firewall and forward logs to a SIEM for correlation analysis

Monitoring Recommendations

• Review web server access logs for requests to /cgi-bin/logs_smtp.cgi with suspicious parameter values
• Monitor for unexpected processes or network connections originating from the Endian Firewall appliance
• Implement file integrity monitoring on critical system files and CGI scripts
• Set up alerts for any administrative actions performed outside of normal maintenance windows

How to Mitigate CVE-2026-34797

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
• Implement strong, unique passwords for all administrative accounts
• Consider disabling the web interface if not actively required and use alternative management methods

Patch Information

At the time of publication, no official patch has been confirmed. Organizations should monitor the Endian Community Help Section for security updates and patch announcements. Until a patch is available, implement the workarounds and mitigations described below.

Workarounds

• Implement network-level access controls to restrict access to the /cgi-bin/logs_smtp.cgi endpoint
• Use a reverse proxy or WAF in front of the Endian Firewall management interface with strict input validation rules
• Limit authentication to the management interface using multi-factor authentication where supported
• Segment the management network to prevent unauthorized access to the firewall administration interface

# Example: Restrict management interface access via iptables (apply on network perimeter)
# Only allow management access from trusted admin subnet
iptables -A INPUT -p tcp --dport 10443 -s 192.168.100.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 10443 -j DROP