CVE-2026-77683: Comfast CF-N1-S Command Injection Vulnerability

CVE-2026-77683 Overview

CVE-2026-77683 is a command injection vulnerability in Comfast CF-N1-S firmware version 2.6.0.1. The flaw resides in the system function called by the /cgi-bin/mbox-config endpoint when handling the method=SET§ion=ntp_timezone request. Attackers manipulate the timestr argument to inject arbitrary operating system commands. The vulnerability is exploitable remotely over the network and requires only low-privilege authentication. Public exploit details have been released, increasing the likelihood of active exploitation against exposed devices. The issue is classified under [CWE-74] (Improper Neutralization of Special Elements in Output Used by a Downstream Component).

Critical Impact
Remote authenticated attackers can execute arbitrary commands on the underlying operating system of Comfast CF-N1-S devices, leading to full device compromise.

Affected Products

Comfast CF-N1-S firmware version 2.6.0.1
The /cgi-bin/mbox-config CGI endpoint
The ntp_timezone configuration section handler

Discovery Timeline

2026-08-21 - CVE-2026-77683 published to NVD
2026-08-24 - Last updated in NVD database

Technical Details for CVE-2026-77683

Vulnerability Analysis

The vulnerability exists in the Comfast CF-N1-S web management interface, specifically in the CGI handler for network time protocol (NTP) timezone configuration. When a client submits a request to /cgi-bin/mbox-config?method=SET§ion=ntp_timezone, the backend passes the user-controlled timestr parameter directly to a system function call without proper neutralization. This allows shell metacharacters such as ;, |, &&, and backticks to break out of the intended command context. Successful exploitation grants command execution under the privileges of the web service, typically root on embedded routers. The attacker gains persistent control over routing, DNS, and traffic inspection capabilities of the device.

Root Cause

The root cause is improper neutralization of special elements passed to a downstream shell interpreter [CWE-74]. The timestr parameter is concatenated into a command string that is then executed through a shell rather than being passed as an argument to a safe execution primitive. No allow-list validation or escaping is applied before invocation.

Attack Vector

Exploitation requires network access to the device's HTTP management interface and low-privilege credentials. An attacker sends a crafted HTTP request to /cgi-bin/mbox-config with the method, section, and malicious timestr parameters. The injected payload executes in the context of the web daemon. Because the exploit has been published, automated scanning and weaponization by opportunistic actors is expected. Details are referenced in the GitHub Issue on CVE-2026-77683 and VulDB Vulnerability Information.

Detection Methods for CVE-2026-77683

Indicators of Compromise

HTTP requests to /cgi-bin/mbox-config containing shell metacharacters (;, |, &, `, $() within the timestr parameter.
Unexpected child processes spawned by the CGI web daemon on the router, such as sh, wget, curl, nc, or busybox invocations.
Outbound connections from the router to unknown hosts shortly after receipt of an NTP timezone configuration request.
New or modified startup scripts, cron entries, or firewall rules on the device following administrative HTTP activity.

Detection Strategies

Inspect web server and reverse proxy logs for POST or GET requests to mbox-config with section=ntp_timezone and non-alphanumeric characters in timestr.
Deploy network signatures on IDS/IPS platforms that flag command injection patterns targeting embedded CGI endpoints.
Correlate management-plane HTTP requests with subsequent DNS lookups or outbound sockets originating from the device.

Monitoring Recommendations

Forward router syslog and HTTP access logs into a centralized analytics platform for long-term retention and correlation.
Alert on any administrative-interface authentication followed by anomalous outbound traffic from the same device.
Baseline expected management traffic and flag deviations in URI paths, parameter length, and payload entropy.

How to Mitigate CVE-2026-77683

Immediate Actions Required

Restrict access to the Comfast CF-N1-S management interface to trusted management VLANs and administrative jump hosts only.
Disable remote WAN-side administration if enabled, and enforce strong, unique credentials for all local accounts.
Audit device configurations and firmware integrity for signs of tampering or unauthorized command execution.
Monitor vendor channels for a firmware update addressing CVE-2026-77683 and apply it promptly when released.

Patch Information

At the time of publication, no vendor advisory or patched firmware version has been identified in the referenced sources. Refer to VulDB CVE Details and the GitHub Issue on CVE-2026-77683 for the latest status. Contact Comfast support directly to confirm remediation availability for firmware 2.6.0.1.

Workarounds

Place the device behind a network segment that blocks inbound HTTP/HTTPS to its management interface from untrusted zones.
Enforce access control lists that permit management traffic only from designated administrator IP addresses.
Rotate administrative credentials and disable unused management accounts to reduce the pool of usable low-privilege identities.
Consider replacing the affected device with a supported model if no patch is released by the vendor.

bash

# Configuration example: restrict management interface with iptables upstream
iptables -A FORWARD -p tcp -d <router_ip> --dport 80 -s <admin_subnet> -j ACCEPT
iptables -A FORWARD -p tcp -d <router_ip> --dport 80 -j DROP
iptables -A FORWARD -p tcp -d <router_ip> --dport 443 -s <admin_subnet> -j ACCEPT
iptables -A FORWARD -p tcp -d <router_ip> --dport 443 -j DROP