CVE-2025-71383

Executive Summary

CVE-2025-71383 affects Dbit WIFI4 N300 version 1.0.0 devices, where the management interface can be remotely crashed by sending a request that omits the username or password field to the /api/login endpoint. The flaw stems from an unhandled error in the JSON parser processing that request, resulting in a denial-of-service (DoS) condition. The attack is exploitable from the local Wi-Fi network (adjacent network vector) without authentication, allowing an attacker already on the wireless segment to render the device's management interface unavailable.

Technical Analysis

The vulnerability resides in the Dbit WIFI4 N300 1.0.0 management interface, specifically in the code path that handles POST requests to the /api/login endpoint. According to the NVD description, the management interface "allow[s] the management interface to be crashed via a request (from the local Wi-Fi network) that lacks a /api/login username or password field." The root cause is "an error in a JSON parser."

This indicates the following mechanism:

• The device's web management application exposes an HTTP API endpoint at /api/login, which expects a JSON body containing at least a username and password field.
• When a request is received that omits one or both of these fields, the JSON parser encounters an unexpected structure (e.g., missing required keys, malformed object) and raises an unhandled exception.
• Because the exception is not caught, the process handling the request—likely the device's web server or management daemon—terminates or enters an unrecoverable state, causing the management interface to become unresponsive.

No further code-level detail (e.g., specific function names, programming language, or parser library) is provided in the NVD description, and no additional technical artifacts are available. The vulnerability is therefore analyzed at the class level: improper input validation (CWE-20) leading to an uncaught exception (CWE-248), which results in a denial-of-service condition.

The attack surface is limited to the local Wi-Fi network (adjacent network). The device does not require authentication to trigger the crash, as the malformed request is processed before any authentication check—the parser error occurs during request parsing, prior to credential verification. This is consistent with the CVSS vector AV:A (Adjacent Network), AC:L (Low complexity), PR:N (No privileges required), UI:N (No user interaction), and A:H (High availability impact).

Exploitation Scenarios

No public proof-of-concept (PoC) or exploit code is available for CVE-2025-71383. The following attack chain is inferred strictly from the vulnerability class and the NVD description. No specific implementation details (function names, HTTP headers, payload byte sequences) are invented; only the endpoint /api/login and the missing username/password fields are referenced because they appear verbatim in the description.

1. Reconnaissance/target identification: An attacker connected to the same Wi-Fi network as the Dbit WIFI4 N300 device identifies the management interface. This can be done by scanning the local subnet for HTTP services (e.g., using Shodan dorks or local network scanning) and locating the login page or API endpoint associated with the device. The attacker notes the IP address of the management interface.

2. Triggering the flaw: The attacker crafts an HTTP POST request to the /api/login endpoint. The request body is intentionally constructed to omit either the username or password field (or both). The request does not need valid credentials; it only needs to reach the JSON parser. The attacker sends this request to the device's management interface.

3. Payload/execution method: Because the JSON parser encounters a structure it does not expect (missing required fields), it raises an error that is not handled by the application. This unhandled exception causes the process serving the management interface to crash or hang. The attacker does not need to deliver a complex payload; simply omitting a required field is sufficient. The exact HTTP method (POST, GET, PUT) is not specified in the description, but the endpoint /api/login implies a POST request for authentication.

4. Post-exploitation impact: The management interface becomes unavailable. Legitimate administrators cannot access the device's configuration or monitoring functions. The device may continue to forward network traffic (if the crash is isolated to the management process), or it may become fully unresponsive if the crashed process is critical. Recovery may require a physical reboot of the device. Repeated exploitation can maintain a persistent denial-of-service condition. No confidentiality or integrity impact is described; the impact is purely availability (A:H).

The attack requires the attacker to be on the local Wi-Fi network (AV:A), meaning the adversary must either be a legitimate network user or have bypassed wireless network access controls. No user interaction is required (UI:N), and no privileges are needed (PR:N) beyond network adjacency.

Impact Assessment

The primary impact is availability: the management interface of the Dbit WIFI4 N300 1.0.0 becomes unusable. This can prevent administrators from reconfiguring the device, applying security updates, or monitoring network status. In a home or small office environment, this could lead to a loss of network management capability, potentially requiring a physical power cycle to restore functionality. If the device is part of a larger network, the DoS could disrupt operations that rely on the device's management plane.

The CVSS vector (CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) reflects:

• Attack Vector (AV:A): Adjacent network—the attacker must be on the same Wi-Fi network.
• Attack Complexity (AC:L): Low—no special conditions are required; a simple malformed request suffices.
• Privileges Required (PR:N): None—no authentication is needed.
• User Interaction (UI:N): None—the attacker does not rely on a victim to perform any action.
• Scope (S:U): Unchanged—the impact is confined to the vulnerable device's management interface.
• Confidentiality (C:N): No confidentiality impact.
• Integrity (I:N): No integrity impact.
• Availability (A:H): High—the management interface is completely unavailable.

The blast radius is limited to the individual device. However, in deployments with multiple Dbit WIFI4 N300 devices, an attacker on the same network segment could sequentially crash each device's management interface. There is no evidence of lateral movement or further compromise beyond the DoS condition.

Detection Guidance

Sigma Rule

title: Dbit WIFI4 N300 Management Interface Crash via Malformed /api/login Request
id: 7a3b9c1e-4f2d-4a8b-9c7e-1d2e3f4a5b6c
status: experimental
description: Detects HTTP requests to /api/login that omit username or password fields, potentially triggering a JSON parser error and crashing the management interface on Dbit WIFI4 N300 1.0.0 devices.
author: Threat Intelligence
date: 2026-01-15
logsource:
  category: webserver
  product: dbit
detection:
  selection_endpoint:
    cs-uri-stem|endswith: '/api/login'
  selection_method:
    cs-method: 'POST'
  filter_valid:
    cs-uri-query|contains:
      - 'username='
      - 'password='
  condition: selection_endpoint and selection_method and not filter_valid
falsepositives:
  - Legitimate clients sending malformed requests due to bugs
level: high
tags:
  - attack.t1190
  - cve.2025.71383

YARA Rule

rule CVE_2025_71383_Dbit_WIFI4_N300_Management_Crash
{
    meta:
        description = "Detects HTTP requests targeting /api/login with missing username or password fields in Dbit WIFI4 N300 1.0.0 management interface"
        author = "Threat Intelligence"
        date = "2026-01-15"
        reference = "CVE-2025-71383"
        severity = "high"

    strings:
        $endpoint = "/api/login" ascii wide nocase
        $json_start = "{" ascii
        $username = "username" ascii wide nocase
        $password = "password" ascii wide nocase

    condition:
        uint16(0) == 0x4854 and // HTTP traffic
        $endpoint and
        $json_start and
        not ($username and $password)
}

Suricata IDS Rule

alert http any any -> any any (msg:"CVE-2025-71383 Dbit WIFI4 N300 Management Interface Crash Attempt (Missing /api/login Credentials)"; flow:to_server,established; http.method; content:"POST"; http.uri; content:"/api/login"; nocase; http.request_body; content:"{"; pcre:"/username|password/i"; negate; sid:1000001; rev:1; metadata:created_at 2026_01_15, cve CVE-2025-71383, confidence High;)

Elastic Detection

sequence by source.ip with maxspan=5s
  [network where event.type == "start" and
   network.protocol == "http" and
   http.request.method == "POST" and
   http.request.uri == "/api/login" and
   not wildcard(http.request.body, "*username*") and
   not wildcard(http.request.body, "*password*")]

Splunk SPL Query

index=web OR index=proxy sourcetype=access_combined OR sourcetype=stream:http
| search http_method=POST uri="/api/login"
| eval has_username=if(like(request_body, "%username%"), 1, 0)
| eval has_password=if(like(request_body, "%password%"), 1, 0)
| where has_username=0 OR has_password=0
| stats count by src_ip, dest_ip, uri, request_body
| sort - count

Wazuh OSSEC Rule

<group name="dbit,wifi4,web,">
  <rule id="100001" level="12">
    <decoded_as>web-accesslog</decoded_as>
    <match>POST /api/login</match>
    <regex>username|password</regex>
    <negate_regex>true</negate_regex>
    <description>CVE-2025-71383: Potential Dbit WIFI4 N300 management interface crash attempt - /api/login without credentials</description>
    <mitre>
      <id>T1190</id>
      <id>T1499</id>
    </mitre>
    <group>cve_2025_71383,availability_attack,</group>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 0/4 (UNPATCHED — no patch evidence from any tracked source).

1. Immediate mitigations:

   • Restrict access to the management interface. Ensure that only trusted, authenticated administrators can reach the device's web management page. Use wireless network access controls (e.g., WPA3, MAC filtering) to limit who can connect to the Wi-Fi network.
   • If the device supports firewall or ACL rules, block external access to the management interface port (typically TCP 80/443) from untrusted local clients.
   • Monitor for repeated requests to /api/login that lack username or password fields, using the detection rules provided above.
   • Consider placing the management interface behind a reverse proxy that performs input validation and rejects malformed requests before they reach the device.

2. Patch/upgrade steps:

   • No vendor patch is currently available. Users should check the Dbit website or contact Dbit support for firmware updates addressing CVE-2025-71383. Until a patch is released, the device remains vulnerable.
   • If the device is no longer supported, consider replacing it with a model that has a track record of security maintenance.

3. Long-term hardening:

   • Segment IoT devices like the Dbit WIFI4 N300 onto a separate VLAN with strict firewall rules limiting communication to only necessary services.
   • Regularly audit firmware versions and apply updates promptly.
   • Implement network-based intrusion detection (using the Suricata rule above) to alert on exploitation attempts.
   • Disable remote management features if they are not required.

References

• NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-71383
• CWE-20: Improper Input Validation — https://cwe.mitre.org/data/definitions/20.html
• CWE-248: Uncaught Exception — https://cwe.mitre.org/data/definitions/248.html
• MITRE ATT&CK T1190: Exploit Public-Facing Application — https://attack.mitre.org/techniques/T1190/
• Vendor website: Dbit (no advisory available). Monitor for future firmware releases addressing this CVE.