CVE-2026-7192

Executive Summary

CVE-2026-7192 is a stack-based buffer overflow (CWE-121) in the Dbit T-CPE301K 4G WiFi minirouter that is triggerable by an authenticated attacker sending an HTTP POST request with an excessively long parameter to the endpoint /js/common/do_cmd.js. Successful exploitation overwrites the saved PC (Program Counter) and RA (Return Address) registers on the stack, causing a denial-of-service condition that reboots the device. The vendor is unknown, no patch exists, and no CVSS, EPSS, or KEV data has been assigned, leaving affected deployments with zero vendor-supplied remediation.

Technical Analysis

The vulnerability is a classic stack-based buffer overflow, classified under CWE-121. According to the NVD description, the flaw resides in the handling of an HTTP POST request directed at the endpoint /js/common/do_cmd.js on the Dbit T-CPE301K 4G WiFi minirouter. When a parameter within that POST request is supplied with excessive length, the receiving code copies the input into a fixed-size stack buffer without adequate bounds checking. The overflow corrupts adjacent stack memory, specifically the saved Program Counter (PC) and Return Address (RA) registers.

In MIPS-class embedded firmware — implied here by the explicit reference to PC and RA registers — the return address register (RA) holds the address to which execution returns after a function call, and the PC is the instruction pointer. Overwriting these values with attacker-controlled data redirects control flow. In this CVE the observed outcome is a denial of service and system reboot, meaning the overwrite leads to an invalid control-flow target, a crash, or a fault that the firmware watchdog handles by restarting the device.

Attack surface and prerequisites:

• The endpoint /js/common/do_cmd.js is reachable over the device's HTTP management interface.
• The attacker must be authenticated, per the NVD description, so a valid session or credential set is required before the overflow can be triggered.
• No specific parameter name is disclosed in the available data, so the exact injection point within the POST body cannot be stated with confidence.

Technical specifics that are NOT available and are therefore not asserted here: the exact stack buffer size, the specific parameter name, the firmware version(s) affected, and the precise overflow offset. These details are absent from the NVD description and no CNA title was provided. The vulnerability class and mechanism are nonetheless clear from the description.

Exploitation Scenarios

No public proof-of-concept, exploit code, or Nuclei template exists for CVE-2026-7192. The attack chain below is inferred at the vulnerability-class level from the NVD description and does not rely on undisclosed implementation details.

1. Reconnaissance / target identification An attacker identifies internet- or LAN-exposed Dbit T-CPE301K minirouters via Shodan or similar scanning, using the management interface fingerprint (HTTP title or the /js/common/do_cmd.js resource path). The target must expose the HTTP management endpoint.

2. Authentication Because the description states the attacker must be authenticated, the adversary obtains valid credentials — through phishing, credential reuse, default-credential guessing, or prior compromise — and establishes an authenticated session against the device's web management interface.

3. Triggering the overflow The attacker crafts an HTTP POST request to /js/common/do_cmd.js and inserts an excessively long value into one of the parameters handled by that endpoint. The over-length input is copied into a fixed-size stack buffer. Because no bounds check stops the copy, the write extends past the buffer boundary and overwrites the saved return address (RA) and program counter (PC) on the stack.

4. Post-exploitation impact The corrupted PC/RA causes execution to jump to an invalid or uncontrolled address, producing a crash. The device detects the fault (e.g., via watchdog) and reboots. The confirmed impact is denial of service and forced system reboot. Whether the overflow can be leveraged beyond DoS into code execution is not established by the available data; the NVD description only specifies DoS and reboot.

Note: There is no public exploit. The chain above is reconstructed from the vulnerability class and the endpoint/parameter behavior described in the NVD entry. Any claim of remote code execution would be speculative and is explicitly not made.

Impact Assessment

CVSS data is not assigned for this CVE (CVSS: N/A from the provided intelligence). A representative vector consistent with a network-reachable, authenticated, stack overflow causing availability loss is CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H, but this is analyst-derived and must not be treated as an official score.

Impact characteristics:

• Confidentiality: none directly established.
• Integrity: none directly established.
• Availability: high — the device reboots and becomes temporarily unreachable.
• Attack vector: network (HTTP management interface).
• Privileges required: low/authenticated (a valid session is required per the description).
• User interaction: none.

Blast radius:

• Small-office, retail, and remote-site deployments using the T-CPE301K 4G WiFi minirouter as their WAN/LAN gateway.
• Repeated exploitation can cause persistent service disruption, defeating the device's role as a connectivity gateway for downstream hosts and clients.
• Because the endpoint is authenticated, the practical attack surface is limited to parties holding credentials, but credential compromise, default credentials, or reuse widens exposure.

Business impact: Loss of connectivity for sites dependent on the router, potential operational downtime, and the cost of manual power-cycling or on-site intervention where the reboot does not self-recover cleanly.

EPSS has not yet been scored by FIRST.org for this CVE, and it is not present in CISA KEV.

Detection Guidance

Sigma Rule

title: Dbit T-CPE301K Stack Buffer Overflow Attempt via do_cmd.js
id: 3f8a1c02-9b5e-4d6a-8c21-dbit7192dos01
status: experimental
description: Detects overly long parameter values in authenticated HTTP POST requests to /js/common/do_cmd.js targeting CVE-2026-7192.
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2026-7192
author: valtersit.com
date: 2026/01/01
logsource:
  category: webserver
  product: generic
detection:
  selection_endpoint:
    cs-uri-stem|contains: '/js/common/do_cmd.js'
  selection_method:
    cs-method: 'POST'
  selection_length:
    cs-uri-query|re: '.{1024,}'
  condition: selection_endpoint and selection_method and selection_length
fields:
  - c-ip
  - cs-uri-stem
  - cs-uri-query
falsepositives:
  - Legitimate administrative commands with unusually large payloads
level: high
tags:
  - attack.t1499
  - cve.2026.7192

YARA Rule

rule CVE_2026_7192_Dbit_do_cmd_Overflow
{
    meta:
        description = "Detects HTTP POST payloads with oversized parameters targeting /js/common/do_cmd.js on Dbit T-CPE301K (CVE-2026-7192)"
        author = "valtersit.com"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-7192"
        date = "2026-01-01"
        severity = "high"

    strings:
        $endpoint = "/js/common/do_cmd.js"
        $method   = "POST "
        $http11   = "HTTP/1.1"
        $http10   = "HTTP/1.0"

    condition:
        uint16(0) == 0x504F or uint16(0) == 0x4745 or $method or
        (
            any of ($http11, $http10) and
            $endpoint and
            $method
        )
}

Note: The YARA rule above is a network/payload-oriented signature. Because no exploit code exists and the exact parameter name is undisclosed, the rule keys on the endpoint path and HTTP method rather than a specific malicious token. Buffer-length heuristics belong in the network detection layer (Suricata) below.

Suricata IDS Rule

alert http any any -> any any (msg:"CVE-2026-7192 Dbit T-CPE301K do_cmd.js Stack Overflow Attempt"; flow:established,to_server; http.method; content:"POST"; http.uri; content:"/js/common/do_cmd.js"; http.request_body; content:"|20|"; pcre:"/.{1024,}/R"; threshold: type limit, track by_src, count 5, seconds 60; classtype:attempted-dos; sid:9007192; rev:1; reference:cve,2026-7192; reference:url,nvd.nist.gov/vuln/detail/CVE-2026-7192;)

Note: The pcre length check is a heuristic for oversized POST bodies associated with the overflow class. Tune {1024,} to the largest legitimate payload observed in the target environment, since the actual stack buffer size is not disclosed.

Elastic Detection

sequence by source.ip with maxspan=30s
  [ network where http.request.method == "POST" and
      url.path == "/js/common/do_cmd.js" and
      network.bytes > 1024 ]

Interpretation: alerts when a single authenticated client issues a POST to /js/common/do_cmd.js carrying an oversized body, indicative of a buffer-overflow attempt against CVE-2026-7192. Adjust network.bytes to reflect legitimate body sizes.

Splunk SPL Query

index=web OR index=proxy
| eval endpoint = coalesce(uri_path, url, cs_uri_stem)
| eval method = coalesce(http_method, cs_method)
| where like(endpoint, "%/js/common/do_cmd.js%") AND method="POST"
| eval body_len = len(coalesce(form_data, request_body, cs_uri_query))
| where body_len > 1024
| stats count min(_time) as first_seen max(_time) as last_seen by src_ip, endpoint
| where count >= 1
| convert ctime(first_seen) ctime(last_seen)
| sort - count

Interpretation: identifies source IPs sending oversized POST requests to the vulnerable endpoint. Tune the 1024 threshold and field names (form_data, request_body) to match your logging pipeline.

Wazuh OSSEC Rule

<group name="web,cve-2026-7192,">
  <rule id="100719" level="10">
    <if_sid>31100</if_sid>
    <match>/js/common/do_cmd.js</match>
    <match>POST</match>
    <description>CVE-2026-7192: POST to vulnerable Dbit T-CPE301K endpoint /js/common/do_cmd.js</description>
    <mitre>
      <id>T1499</id>
    </mitre>
    <group>cve_2026_7192,</group>
  </rule>

  <rule id="100720" level="12">
    <if_sid>100719</if_sid>
    <regex>\.{1024,}</regex>
    <description>CVE-2026-7192: Oversized parameter in do_cmd.js request - possible stack buffer overflow</description>
    <group>cve_2026_7192,</group>
  </rule>
</group>

Note: Rule 31100 is the standard Wazuh web-access-log decoder parent; adjust parent SIDs to your deployed decoder set. The regex length check is a heuristic because the exact overflow threshold is undisclosed.

Mitigation & Patch Guidance

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

1. Immediate mitigations

• Isolate the router management interface from untrusted networks; never expose /js/common/do_cmd.js or the management UI to the internet.
• Restrict administrative access to a trusted management VLAN and enforce strong, unique credentials; rotate any default credentials immediately.
• Where feasible, place the device behind a firewall/WAF rule that rejects POST requests to /js/common/do_cmd.js with bodies exceeding a sane length, or blocks the endpoint entirely if unused.
• Monitor for repeated reboots or unexpected device restarts, which may indicate active exploitation.
• Apply the Suricata/Sigma/Wazuh detections above at the network perimeter and host log layer.

2. Patch / upgrade steps

• No vendor fix exists. Contact the vendor/manufacturer (Dbit) or the reseller to request a firmware update and a CVE-assigned fix.
• If no patch is forthcoming, evaluate replacement with a supported 4G/LTE router that receives security updates.
• Track the NVD entry (CVE-2026-7192) for a future patch reference; none is currently published.

3. Long-term hardening

• Establish a vulnerability-management process covering embedded network gear, including periodic firmware review.
• Segment OT/IoT/edge devices onto isolated network zones with strict egress and ingress filtering.
• Disable unused management endpoints and services on all edge devices.
• Enforce credential hygiene and multi-factor authentication on management interfaces where supported.

References

1. NVD — CVE-2026-7192: https://nvd.nist.gov/vuln/detail/CVE-2026-7192
2. CWE-121 — Stack-based Buffer Overflow: https://cwe.mitre.org/data/definitions/121.html
3. MITRE ATT&CK — T1499 Endpoint Denial of Service: https://attack.mitre.org/techniques/T1499/
4. FIRST EPSS (no score currently assigned for this CVE): https://www.first.org/epss/
5. CISA Known Exploited Vulnerabilities Catalog (CVE not listed): https://www.cisa.gov/known-exploited-vulnerabilities-catalog

Threat actor context: No known threat actor campaigns and no exploit-in-the-wild evidence are associated with CVE-2026-7192 at this time. No public PoC, exploit code, or Nuclei template has been published, and the CVE is not present in CISA KEV.