CVE-2025-34035: EnGeniusTech ESR300 Firmware RCE Vulnerability

CVE-2025-34035 Overview

CVE-2025-34035 is a critical OS command injection vulnerability affecting EnGenius EnShare Cloud Service version 1.4.11 and earlier. The vulnerability exists in the usbinteract.cgi script, which fails to properly sanitize user input passed to the path parameter. This flaw allows unauthenticated remote attackers to inject arbitrary shell commands that are executed with root privileges, leading to complete system compromise.

This vulnerability is particularly severe as it requires no authentication and can be exploited remotely over the network. The Shadowserver Foundation observed exploitation evidence on 2024-12-05, indicating active threat actor interest in this vulnerability.

Critical Impact

Unauthenticated remote command execution with root privileges enables full device takeover, potentially allowing attackers to pivot into internal networks, exfiltrate data, or deploy malware on compromised routers.

Affected Products

• EnGenius ESR300 Firmware (versions up to 1.4.9)
• EnGenius ESR350 Firmware (versions up to 1.4.11)
• EnGenius ESR600 Firmware (versions up to 1.4.11)
• EnGenius ESR900 Firmware (versions up to 1.4.5)
• EnGenius ESR1200 Firmware (versions up to 1.4.5)
• EnGenius ESR1750 Firmware (versions up to 1.4.5)
• EnGenius EPG5000 Firmware (versions up to 1.3.9.21)

Discovery Timeline

• 2024-12-05 - Exploitation evidence observed by Shadowserver Foundation
• 2025-06-24 - CVE CVE-2025-34035 published to NVD
• 2025-11-20 - Last updated in NVD database

Technical Details for CVE-2025-34035

Vulnerability Analysis

The vulnerability resides in the usbinteract.cgi script within the EnGenius EnShare Cloud Service web interface. This script handles USB device interactions and accepts a path parameter from user requests. Due to insufficient input validation and sanitization, user-supplied data in the path parameter is passed directly to shell commands without proper escaping or filtering.

The attack can be executed by an unauthenticated remote attacker who crafts a malicious HTTP request to the vulnerable CGI endpoint. Since the web server process runs with elevated privileges, any injected commands execute as root on the underlying Linux-based operating system. This grants attackers complete control over the affected device.

Root Cause

The root cause is improper input validation (CWE-78: OS Command Injection). The usbinteract.cgi script constructs shell commands by directly concatenating user input from the path parameter without sanitizing or escaping shell metacharacters. This design flaw allows attackers to break out of the intended command context and inject arbitrary commands using shell metacharacters such as semicolons (;), pipes (|), backticks (`), or command substitution syntax ($()).

Attack Vector

The attack vector is network-based and requires no authentication or user interaction. An attacker can exploit this vulnerability by sending a specially crafted HTTP request to the vulnerable usbinteract.cgi endpoint on an exposed EnGenius router. The malicious request includes shell commands embedded within the path parameter.

A typical exploitation scenario involves:

1. Identifying an exposed EnGenius device running a vulnerable firmware version
2. Sending an HTTP request to /usbinteract.cgi with a malicious path parameter containing shell metacharacters and commands
3. The injected commands execute with root privileges on the target device
4. The attacker gains full control and can install backdoors, modify configurations, or use the device for further attacks

For detailed exploitation techniques and proof-of-concept code, refer to Exploit-DB #42114 and Zero Science Lab Advisory ZSL-2017-5413.

Detection Methods for CVE-2025-34035

Indicators of Compromise

• Unusual HTTP requests to /usbinteract.cgi containing shell metacharacters such as ;, |, &, `, $() in the path parameter
• Unexpected outbound network connections from EnGenius router devices to unknown external IP addresses
• New or modified system files, particularly in /tmp, /var, or other writable directories on the router
• Unexplained changes to router configuration or admin credentials
• Evidence of reverse shells or persistent backdoor processes running on the device

Detection Strategies

• Monitor web server access logs on EnGenius devices for requests to usbinteract.cgi with suspicious parameter values
• Deploy network intrusion detection rules to identify HTTP requests containing OS command injection patterns targeting EnGenius devices
• Implement behavioral analysis to detect anomalous outbound connections from IoT/network devices
• Use SentinelOne Singularity to monitor network endpoints for communication with known malicious infrastructure

Monitoring Recommendations

• Enable logging on EnGenius devices and forward logs to a centralized SIEM for correlation and analysis
• Set up alerts for any access attempts to CGI endpoints from external IP addresses
• Monitor for firmware integrity changes using file integrity monitoring solutions where applicable
• Track EPSS score trends (currently 7.63% probability, 91.73 percentile) as an indicator of exploitation likelihood

How to Mitigate CVE-2025-34035

Immediate Actions Required

• Restrict network access to the EnGenius device management interface to trusted internal networks only; do not expose management interfaces to the internet
• Implement firewall rules to block external access to HTTP/HTTPS ports on affected devices
• Audit network logs for evidence of prior exploitation attempts targeting usbinteract.cgi
• Consider taking vulnerable devices offline until firmware updates are applied or replacement devices are deployed
• Segment affected devices from critical network infrastructure to limit lateral movement potential

Patch Information

EnGenius has not released an official security advisory with patch information at the time of this publication. Organizations should monitor the VulnCheck Advisory on EnGenius and the vendor's support page for firmware updates addressing this vulnerability. Given the age of the affected device models, some may have reached end-of-life status without available patches.

Workarounds

• Disable the EnShare Cloud Service feature if it is not required for business operations
• Configure access control lists (ACLs) on the router to restrict access to the web management interface from specific trusted IP addresses only
• Place affected routers behind a firewall that blocks unsolicited inbound HTTP requests to management interfaces
• Consider replacing end-of-life devices with currently supported hardware that receives security updates
• Use a VPN for remote management access rather than exposing the management interface directly

# Example iptables rule to restrict access to management interface
# Apply on upstream firewall or router
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP