CVE-2026-4466: Comfast CF-AC100 RCE Vulnerability

CVE-2026-4466 Overview

A command injection vulnerability has been identified in Comfast CF-AC100 firmware version 2.6.0.8. This vulnerability affects an unknown function within the file /cgi-bin/mbox-config?method=SET§ion=ntp_timezone. Through manipulation of input parameters, an attacker can inject arbitrary commands that are executed on the underlying system. The vulnerability can be exploited remotely over the network, and exploit code has been publicly disclosed. The vendor was contacted regarding this disclosure but did not respond.

Critical Impact

Remote attackers with administrative privileges can execute arbitrary commands on the Comfast CF-AC100 router, potentially leading to full device compromise, network pivoting, or persistent backdoor installation.

Affected Products

• Comfast CF-AC100 firmware version 2.6.0.8

Discovery Timeline

• 2026-03-20 - CVE-2026-4466 published to NVD
• 2026-03-20 - Last updated in NVD database

Technical Details for CVE-2026-4466

Vulnerability Analysis

This vulnerability is classified as CWE-74 (Improper Neutralization of Special Elements in Output Used by a Downstream Component), commonly known as injection. The affected endpoint /cgi-bin/mbox-config?method=SET§ion=ntp_timezone fails to properly sanitize user-supplied input before incorporating it into system commands.

The attack requires network access and high-level privileges (administrative access), which limits the attack surface somewhat. However, once an attacker has authenticated access to the router's administrative interface, they can leverage this vulnerability to execute arbitrary commands with the privileges of the web server process, typically root on embedded devices like this router.

Root Cause

The root cause of this vulnerability is improper input validation in the NTP timezone configuration handler. The CGI script responsible for processing the ntp_timezone section parameters does not adequately filter or escape special characters and command injection payloads. User input is likely passed directly to a shell command or system call without proper sanitization, allowing metacharacters such as semicolons, pipes, or backticks to break out of the intended command context.

Attack Vector

The attack is network-based and requires the attacker to have authenticated administrative access to the Comfast CF-AC100 device. The exploitation flow involves:

1. An attacker authenticates to the device's administrative web interface
2. The attacker crafts a malicious HTTP request to the vulnerable endpoint /cgi-bin/mbox-config?method=SET§ion=ntp_timezone
3. Command injection payloads are embedded within the request parameters
4. The vulnerable CGI script processes the request and executes the injected commands
5. The attacker gains command execution on the underlying embedded Linux system

The vulnerability exploitation details have been publicly disclosed. For technical specifics, refer to the GitHub CVE Documentation and VulDB CVE Analysis #351756.

Detection Methods for CVE-2026-4466

Indicators of Compromise

• Unusual HTTP requests to /cgi-bin/mbox-config containing shell metacharacters (;, |, $(), backticks)
• Unexpected outbound network connections from the router to external IP addresses
• Unauthorized processes running on the device, particularly reverse shells or download utilities
• Modification of system files or configuration outside normal administrative actions

Detection Strategies

• Monitor web server logs on the CF-AC100 for suspicious requests to the mbox-config endpoint containing injection patterns
• Deploy network intrusion detection signatures targeting command injection patterns in HTTP requests to IoT devices
• Implement egress filtering to detect unusual outbound connections from network infrastructure devices
• Utilize SentinelOne Singularity to monitor for anomalous process execution patterns on network segments containing vulnerable devices

Monitoring Recommendations

• Enable and centralize logging from all Comfast CF-AC100 devices
• Configure alerts for authentication attempts and configuration changes on network infrastructure devices
• Implement network traffic analysis to detect command-and-control communications from compromised routers
• Regularly audit administrative access logs for unauthorized access attempts

How to Mitigate CVE-2026-4466

Immediate Actions Required

• Restrict administrative access to the CF-AC100 to trusted IP addresses only using firewall rules
• Ensure administrative credentials are strong and unique; do not use default credentials
• Place the device's management interface on an isolated management VLAN inaccessible from untrusted networks
• Consider temporarily disabling remote administration if not required
• Monitor network traffic for exploitation attempts

Patch Information

The vendor (Comfast) was contacted regarding this vulnerability but did not respond. As of the last NVD update on 2026-03-20, no official patch is available. Users should monitor the VulDB entry and vendor channels for any future security updates.

Workarounds

• Implement strict network segmentation to isolate vulnerable devices from untrusted networks
• Use a firewall or access control list to restrict access to the device's web interface to only necessary management hosts
• Consider deploying a web application firewall (WAF) in front of the device if architecturally feasible
• Replace the device with a supported alternative if no patch becomes available
• Implement strong authentication and consider multi-factor authentication for network device management

# Example: Restrict administrative access via iptables on upstream firewall
# Allow only management subnet to access CF-AC100 web interface
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 80 -s 10.0.0.0/24 -j ACCEPT
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 80 -j DROP
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 443 -s 10.0.0.0/24 -j ACCEPT
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 443 -j DROP