CVE-2026-2537: Comfast CF-E4 RCE Vulnerability

CVE-2026-2537 Overview

A command injection vulnerability has been identified in Comfast CF-E4 version 2.6.0.1. This vulnerability affects an unknown function within the file /cgi-bin/mbox-config?method=SET§ion=ntp_timezone of the HTTP POST Request Handler component. Manipulation of the timestr argument enables command injection, allowing attackers to execute arbitrary system commands on the affected device. The attack can be launched remotely, and a public exploit is available. The vendor was contacted about this vulnerability but did not respond.

Critical Impact
Remote attackers with administrative access can execute arbitrary commands on affected Comfast CF-E4 devices through the NTP timezone configuration endpoint, potentially leading to complete device compromise.

Affected Products

Comfast CF-E4 version 2.6.0.1
Comfast CF-E4 devices with vulnerable HTTP POST Request Handler

Discovery Timeline

2026-02-16 - CVE CVE-2026-2537 published to NVD
2026-02-18 - Last updated in NVD database

Technical Details for CVE-2026-2537

Vulnerability Analysis

This vulnerability is classified under CWE-74 (Improper Neutralization of Special Elements in Output Used by a Downstream Component), which encompasses injection flaws. The affected endpoint /cgi-bin/mbox-config?method=SET§ion=ntp_timezone processes user-supplied input through the timestr parameter without proper sanitization or validation. When an authenticated administrator sends a crafted HTTP POST request to this endpoint, the device fails to neutralize shell metacharacters or command separators in the timestr value before passing it to system command execution functions.

The vulnerability requires network access and high privileges (administrative credentials), which somewhat limits the attack surface. However, given that many embedded devices use default or weak credentials, this requirement may not provide significant protection in practice. The exploitation of this flaw could allow an attacker to execute arbitrary commands with the privileges of the web server process, typically running as root on embedded Linux systems.

Root Cause

The root cause lies in insufficient input validation within the NTP timezone configuration handler. The timestr parameter is directly incorporated into system commands without proper sanitization, escaping, or use of parameterized APIs. This allows command injection through shell metacharacters such as semicolons, backticks, or command substitution syntax.

Attack Vector

The attack is network-based and targets the HTTP POST Request Handler component. An attacker with administrative credentials can craft a malicious HTTP POST request to the /cgi-bin/mbox-config endpoint, setting the method parameter to SET and section to ntp_timezone. By injecting shell commands into the timestr argument using command separators or substitution syntax, the attacker can execute arbitrary commands on the underlying operating system.

The vulnerability manifests when the device processes NTP timezone configuration requests. The timestr parameter value is passed to a system command without proper sanitization, enabling command injection. Technical details and exploitation methodology are documented in the GitHub RCE Documentation.

Detection Methods for CVE-2026-2537

Indicators of Compromise

Unusual HTTP POST requests to /cgi-bin/mbox-config with suspicious timestr parameter values containing shell metacharacters
Unexpected processes spawned by the web server on Comfast CF-E4 devices
Anomalous outbound network connections from the device indicating potential reverse shell activity
Modified system files or new user accounts on the device

Detection Strategies

Monitor HTTP traffic for POST requests to /cgi-bin/mbox-config?method=SET§ion=ntp_timezone containing shell metacharacters (;, |, $(), backticks) in the timestr parameter
Implement network intrusion detection rules to identify command injection patterns in HTTP traffic to Comfast devices
Deploy application-layer firewalls or WAF rules to block requests with suspicious payloads targeting the vulnerable endpoint
Review web server access logs for repeated authentication attempts followed by requests to the NTP configuration endpoint

Monitoring Recommendations

Enable verbose logging on network edge devices monitoring traffic to embedded IoT devices
Establish baseline network behavior for Comfast CF-E4 devices and alert on deviations
Monitor for DNS queries or connection attempts to unknown external hosts from the device

How to Mitigate CVE-2026-2537

Immediate Actions Required

Restrict network access to the administrative interface of affected Comfast CF-E4 devices using firewall rules or network segmentation
Ensure strong, unique administrative credentials are configured on all affected devices
Place affected devices behind a VPN or authenticated reverse proxy to limit exposure
Consider isolating affected devices on a dedicated VLAN with restricted internet access

Patch Information

At the time of publication, the vendor (Comfast) has not responded to disclosure attempts and no official patch is available. Organizations should monitor vendor communications and the VulDB entry for updates regarding patch availability.

Workarounds

Implement network-level access controls to restrict access to the device management interface to trusted IP addresses only
Disable remote administration if not required, or limit it to internal network access
Deploy a web application firewall (WAF) in front of the device to filter malicious requests
Monitor the device for signs of compromise and consider replacement with a device from a vendor with active security support

bash

# Example: Restrict access to device management interface using iptables on a gateway
# Allow only trusted management network to access device on port 80/443
iptables -A FORWARD -d <device_ip> -p tcp --dport 80 -s <trusted_network>/24 -j ACCEPT
iptables -A FORWARD -d <device_ip> -p tcp --dport 443 -s <trusted_network>/24 -j ACCEPT
iptables -A FORWARD -d <device_ip> -p tcp --dport 80 -j DROP
iptables -A FORWARD -d <device_ip> -p tcp --dport 443 -j DROP