CVE-2026-78796

Executive Summary

CVE-2026-78796 is a critical remote code execution vulnerability affecting Netcore B11 Enterprise-level full Gigabit 9-port shop wireless routers running firmware version v1.3.241114.024540 and earlier. The flaw resides in the www\cgi-bin\upgrade component, allowing an unauthenticated remote attacker to execute arbitrary code on the affected device. Successful exploitation grants full control of the router, enabling network traffic manipulation, credential theft, and lateral movement into the connected internal network.

Technical Analysis

The vulnerability is classified as an arbitrary code execution flaw (CWE-78, OS Command Injection) within the www\cgi-bin\upgrade file — a CGI handler responsible for processing firmware upgrade requests on Netcore B11 routers. Based on the NVD description, a remote attacker can trigger this vulnerability without authentication, as the www\cgi-bin\upgrade endpoint is part of the device's web management interface.

The attack surface is the router's HTTP/HTTPS management interface, specifically the firmware upgrade functionality. Firmware upgrade handlers commonly accept uploaded files or parameters specifying upgrade sources. In this case, the description indicates that the www\cgi-bin\upgrade file does not properly sanitize or validate user-supplied input before passing it to a system-level execution context. This allows an attacker to inject arbitrary commands that are executed with the privileges of the CGI process — typically root on embedded Linux-based router firmware.

The mechanism is consistent with OS command injection, where attacker-controlled input is concatenated into a shell command string executed via system(), popen(), or similar functions within the CGI binary. Because the exact parameter names and injection points are not disclosed in the available intelligence, the specific input vector cannot be confirmed beyond the file path www\cgi-bin\upgrade. No public proof-of-concept, exploit code, or Nuclei template is currently available, meaning exploitation details remain theoretical and inferred from the vulnerability class.

The CVSS vector reflects a pre-authentication, network-accessible flaw with high confidentiality, integrity, and availability impact (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H). The lack of authentication requirements and low attack complexity make this a high-severity target for automated scanning and exploitation. The affected firmware version v1.3.241114.024540 and earlier indicates a broad installed base of enterprise and small-business routers deployed as primary gateway devices.

Exploitation Scenarios

No public PoC or exploit code is available for CVE-2026-78796. The following attack chain is inferred strictly from the NVD description and the vulnerability class (OS command injection in a CGI firmware upgrade handler):

1. Reconnaissance / Target Identification: An attacker scans the internet for exposed Netcore B11 router management interfaces using Shodan (e.g., http.title:"Netcore" or http.html:"Netcore"). Devices with the web management interface reachable from untrusted networks (WAN-side exposed or improperly segmented management VLANs) are identified as candidate targets.

2. Vulnerability Triggering: The attacker sends a crafted HTTP request to the www\cgi-bin\upgrade endpoint on the target router. The request includes malicious input designed to break out of the intended firmware upgrade command context and inject OS-level commands. Because the vulnerability is unauthenticated, no credentials are required.

3. Payload Execution: The injected commands are executed by the CGI process on the underlying embedded operating system, typically with root or high-level privileges. The attacker can leverage this to download and execute a second-stage payload (e.g., shell script, reverse shell binary, or cryptocurrency miner) from a remote server.

4. Post-Exploitation Impact: With code execution on the router, the attacker gains complete control over the device. This enables persistent access, manipulation of network traffic (DNS hijacking, traffic redirection), interception of credentials transmitted over the local network, use of the router as a botnet node or proxy, and lateral movement into the connected internal network. The router's position as a gateway device makes it a high-value pivot point for further attacks.

Impact Assessment

The impact of CVE-2026-78796 is severe. As an unauthenticated remote code execution vulnerability in a network edge device, it carries a CVSS base score consistent with critical severity (inferred CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H). The high confidentiality, integrity, and availability subscores reflect the attacker's ability to read sensitive data (network traffic, credentials), modify system behavior (redirect traffic, alter configurations), and disrupt operations (disable the device, cause outages).

Affected systems are Netcore B11 Enterprise-level full Gigabit 9-port shop wireless routers running firmware v1.3.241114.024540 and earlier. These devices are commonly deployed in retail shops, small businesses, and branch offices — environments where they serve as the primary internet gateway and Wi-Fi access point. The blast radius includes not only the router itself but all downstream devices and users whose traffic traverses the compromised gateway.

Business impact includes potential data breaches, service disruption, regulatory compliance violations (if sensitive data is intercepted), and reputational damage. The lack of a vendor patch (patch confidence 0/4) means organizations relying on these devices remain exposed until mitigations are applied or the hardware is replaced.

Detection Guidance

Sigma Rule

title: Netcore B11 Router Arbitrary Code Execution via CGI Upgrade Endpoint
id: 6b4a9d3e-2f7c-4e8a-9b1d-3c5e7a9f2d4b
status: experimental
description: Detects exploitation attempts targeting CVE-2026-78796 in Netcore B11 routers via the www/cgi-bin/upgrade endpoint
author: Threat Intelligence
date: 2026-01-01
logsource:
  category: webserver
  product: netcore
detection:
  selection_endpoint:
    cs-uri-stem|contains: '/cgi-bin/upgrade'
  selection_methods:
    cs-method:
      - 'POST'
      - 'PUT'
  selection_suspicious:
    cs-uri-query|contains:
      - ';'
      - '|'
      - '`'
      - '$('
      - '../'
  condition: selection_endpoint and selection_methods and selection_suspicious
falsepositives:
  - Legitimate firmware upgrade operations with unusual filenames (rare)
level: high
tags:
  - attack.t1190
  - cve.2026.78796

YARA Rule

rule CVE_2026_78796_Netcore_B11_RCE
{
    meta:
        description = "Detects exploitation attempts against CVE-2026-78796 in Netcore B11 firmware upgrade handler"
        author = "Threat Intelligence"
        date = "2026-01-01"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-78796"
        severity = "critical"

    strings:
        $endpoint = "www\\cgi-bin\\upgrade" nocase
        $endpoint2 = "cgi-bin/upgrade" nocase
        $cmd1 = ";/bin/sh" nocase
        $cmd2 = "|/bin/sh" nocase
        $cmd3 = "`wget" nocase
        $cmd4 = "$(wget" nocase
        $cmd5 = "curl -o" nocase
        $cmd6 = "chmod +x" nocase

    condition:
        ($endpoint or $endpoint2) and any of ($cmd*)
}

Suricata IDS Rule

alert http any any -> any any (msg:"CVE-2026-78796 Netcore B11 Router Arbitrary Code Execution Attempt via CGI Upgrade"; flow:established,to_server; http.uri; content:"/cgi-bin/upgrade"; http.method; content:"POST"; pcre:"/(\;|\||\`|\$\(|\.\.\/)/Ui"; classtype:attempted-admin; sid:202678796; rev:1; reference:cve,2026-78796; reference:url,https://nvd.nist.gov/vuln/detail/CVE-2026-78796; metadata:service http;)

Elastic Detection

network where
  http.request.method == "POST" and
  stringContains(http.request.path, "/cgi-bin/upgrade") and
  (stringContains(http.request.body, ";") or
   stringContains(http.request.body, "|") or
   stringContains(http.request.body, "`") or
   stringContains(http.request.body, "$("))

Splunk SPL Query

index=web OR index=network
(uri_path="/cgi-bin/upgrade" OR uri="*cgi-bin/upgrade*")
(http_method="POST" OR http_method="PUT")
| regex uri="(?i)(;|\||`|\$\(|\.\.\/)"
| stats count min(_time) as first_seen max(_time) as last_seen by src_ip, dest_ip, uri, http_method, user_agent
| where count > 0
| sort - count

Wazuh OSSEC Rule

<group name="netcore,cve-2026-78796,web,">
  <rule id="100796" level="12">
    <decoded_as>web-accesslog</decoded_as>
    <field name="url">/cgi-bin/upgrade</field>
    <field name="method">POST</field>
    <regex offset="after_parent">(\;|\||`|\$\(|\.\.\/)</regex>
    <description>CVE-2026-78796: Netcore B11 router arbitrary code execution attempt via CGI upgrade endpoint</description>
    <mitre>
      <id>T1190</id>
    </mitre>
    <group>cve_2026_78796,attack.initial_access,</group>
  </rule>
</group>

Mitigation & Patch Guidance

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

1. Immediate Mitigations:

   • Disable remote WAN-side access to the router's web management interface. Ensure the www\cgi-bin\upgrade endpoint is only reachable from a trusted, internal management VLAN.
   • Restrict access to the router management interface via firewall rules, allowing only specific administrative IP addresses.
   • Deploy network-level detection rules (Suricata, Wazuh) to alert on suspicious POST requests to /cgi-bin/upgrade.
   • Monitor for anomalous outbound connections from the router that may indicate command-and-control traffic or second-stage payload downloads.

2. Patch/Upgrade Steps:

   • No vendor patch is currently available. Contact Netcore support directly to inquire about a firmware update addressing CVE-2026-78796.
   • Monitor the Netcore website and NVD entry for updated firmware releases.
   • If a patched firmware version becomes available, apply it immediately following vendor instructions.

3. Long-Term Hardening:

   • Replace end-of-life or unpatched router hardware with devices from vendors that maintain active security update programs.
   • Implement network segmentation to isolate IoT and edge devices from critical internal assets.
   • Enforce a strict egress filtering policy to limit the ability of compromised devices to communicate with external command-and-control infrastructure.
   • Conduct regular firmware audits and vulnerability scans of all network edge devices.
   • Enable centralized logging and monitoring for all router management interfaces.

References

• NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-78796
• Netcore Official Website: https://www.netcore.in/
• CWE-78: Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection'): https://cwe.mitre.org/data/definitions/78.html
• MITRE ATT&CK T1190 — Exploit Public-Facing Application: https://attack.mitre.org/techniques/T1190/
• CISA Known Exploited Vulnerabilities Catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog (CVE-2026-78796 not currently listed)