CVE-2026-2535: Comfast CF-N1 Firmware RCE Vulnerability

CVE-2026-2535 Overview

CVE-2026-2535 is a command injection vulnerability affecting Comfast CF-N1 wireless devices running firmware version 2.6.0.2. The flaw resides in the sub_44AB9C function within the /cgi-bin/mbox-config?method=SET§ion=ptest_channel endpoint. Attackers can manipulate the channel argument to inject arbitrary operating system commands. The attack can be launched remotely over the network with low-privilege authentication. Public exploit details have been disclosed, and the vendor did not respond to disclosure attempts. The vulnerability is categorized under [CWE-74] Improper Neutralization of Special Elements in Output and [CWE-77] Improper Neutralization of Special Elements used in a Command.

Critical Impact

Authenticated remote attackers can inject operating system commands through the channel parameter of the ptest_channel configuration endpoint, leading to unauthorized command execution on affected Comfast CF-N1 devices.

Affected Products

• Comfast CF-N1 hardware revision 2
• Comfast CF-N1 firmware version 2.6.0.2
• Devices exposing the /cgi-bin/mbox-config management interface

Discovery Timeline

• 2026-02-16 - CVE-2026-2535 published to NVD
• 2026-04-29 - Last updated in NVD database

Technical Details for CVE-2026-2535

Vulnerability Analysis

The vulnerability exists in the CGI handler responsible for processing wireless channel configuration requests on the Comfast CF-N1 access point. The sub_44AB9C function processes the channel parameter supplied through the /cgi-bin/mbox-config?method=SET§ion=ptest_channel URI without sufficient input neutralization. An authenticated attacker who can reach the device's management interface can append shell metacharacters to the channel argument. The injected payload executes within the context of the CGI process, which typically runs with elevated privileges on embedded routers. Successful exploitation grants attackers the ability to run arbitrary commands, modify device configuration, and pivot into adjacent network segments.

Root Cause

The root cause is improper neutralization of special elements used in operating system commands [CWE-77]. The sub_44AB9C function passes user-controlled input from the channel HTTP parameter directly to a system shell invocation without sanitization or argument escaping. Embedded firmware commonly relies on system() or popen() style calls to wrap utilities such as iwconfig or vendor-specific channel-setting binaries, and any unsanitized concatenation enables command injection.

Attack Vector

The attack is remote and requires low-privilege authentication. An attacker sends a crafted HTTP request to the mbox-config CGI endpoint with a malicious channel value containing shell separators such as ;, &&, or backticks followed by an arbitrary command. The device parses the request, invokes the underlying shell command, and executes the injected payload. According to public disclosure, working exploit details have been made public. See the GitHub CVE Analysis and VulDB entry #346123 for the technical write-up.

Detection Methods for CVE-2026-2535

Indicators of Compromise

• HTTP requests to /cgi-bin/mbox-config containing section=ptest_channel with shell metacharacters such as ;, |, &, or backticks in the channel parameter.
• Unexpected outbound network connections originating from the CF-N1 device to attacker-controlled infrastructure.
• Unauthorized modifications to device configuration files or the presence of new processes spawned by the CGI handler.

Detection Strategies

• Inspect web server and CGI access logs on the device for requests targeting mbox-config with abnormal channel argument values.
• Deploy network-based intrusion detection signatures matching command injection patterns in HTTP query strings to embedded device management endpoints.
• Correlate authentication events against the management interface with subsequent administrative configuration requests to identify suspicious sequences.

Monitoring Recommendations

• Restrict and monitor all traffic destined for the CF-N1 management interface, alerting on access from non-administrative source addresses.
• Capture and review HTTP request bodies and query strings to the /cgi-bin/ path for shell metacharacters and encoded variants.
• Forward device syslog output to a centralized logging platform and alert on unusual process invocations following CGI requests.

How to Mitigate CVE-2026-2535

Immediate Actions Required

• Remove the Comfast CF-N1 management interface from public network exposure and restrict access to a trusted administrative VLAN.
• Change default administrative credentials and enforce strong, unique passwords to limit the pool of attackers with the required low privilege.
• Audit existing devices for signs of compromise, including unexpected configuration changes or unknown outbound connections.

Patch Information

No vendor patch is available at the time of publication. According to the NVD record, the vendor was contacted but did not respond to the disclosure. Organizations operating affected hardware should consider replacing the devices with supported alternatives or isolating them from sensitive network segments. Monitor the VulDB advisory for any future vendor response.

Workarounds

• Place CF-N1 devices behind a firewall that blocks inbound access to the HTTP management interface from untrusted networks.
• Disable remote management features where supported and require administrative access through an out-of-band or VPN-protected channel.
• Segment wireless infrastructure so that a compromised access point cannot reach internal management systems or sensitive data.

# Configuration example: restrict management interface access with iptables
iptables -A INPUT -p tcp --dport 80 -s 10.10.10.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -s 10.10.10.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP