CVE-2026-108907

Executive Summary

CVE-2026-108907 is a critical improper authentication vulnerability in the Netcore NR268 router (version 1.7.121109) affecting the user_ok function within a CGI execution component. A remote, unauthenticated attacker can exploit this flaw to bypass authentication controls, potentially gaining full device control, with a maximum CVSS score of 10.0. The exploit has been publicly disclosed and exploitation attempts may be imminent, yet no vendor patch or workaround exists.

Technical Analysis

The vulnerability resides in the user_ok function of a CGI (Common Gateway Interface) component within the Netcore NR268 firmware. CGI scripts are commonly used in embedded devices like routers to handle web-based management interfaces. The user_ok function likely serves as an authentication check—verifying user-provided credentials before granting access to administrative functionalities.

CWE-287 (Improper Authentication) indicates that the authentication mechanism is fundamentally flawed, allowing an attacker to bypass it entirely. The NVD description states "improper authentication" and that the flaw is remotely triggerable without authentication (CVSS vector: AV:N/AC:L/PR:N/UI:N). The scope change (S:C) in the CVSS vector implies the vulnerable component (the CGI authentication routine) impacts other components (e.g., the underlying operating system, network stack, or configuration database), leading to full compromise of confidentiality, integrity, and availability.

Given the lack of detailed technical disclosure, the exact bypass method (e.g., authentication logic flaw, missing credential validation, hardcoded credentials, or session manipulation) cannot be confirmed. However, the function name user_ok strongly suggests a routine that returns a boolean authentication result. Common implementation errors in such functions include: failing to validate credentials under certain request conditions (e.g., specific HTTP headers, request methods, or parameter absence), or using unsafe string comparisons that can be bypassed. Without vendor confirmation, these remain hypotheses consistent with the vulnerability class.

The attack surface is the router's web management interface, accessible via HTTP/HTTPS on the local network or, if exposed, the internet. The CGI script handling authentication can be reached remotely, and the flaw allows an attacker to skip authentication entirely.

Exploitation Scenarios

No public proof-of-concept (PoC) or exploit code is available; the attack chain is inferred from the vulnerability class (improper authentication) and the NVD description.

1. Reconnaissance/Target Identification: An attacker scans the internet or local network for Netcore NR268 devices, typically via Shodan dorks like product:"Netcore NR268" or by probing common management ports (80, 443, 8080). Fingerprinting the web interface or HTTP response headers can confirm the device model and firmware version.

2. Triggering the Flaw: The attacker sends a crafted HTTP request to the vulnerable CGI endpoint that invokes the user_ok function. Because authentication is improperly implemented, the request bypasses credential checks—likely by omitting authentication parameters, using a malformed request, or exploiting a logic error in the function's decision flow. The exact request structure is unknown, but the flaw is in the authentication function itself, meaning the bypass occurs at the point of authentication evaluation.

3. Payload/Execution Method: Once authentication is bypassed, the attacker gains access to administrative CGI functions. They can then issue legitimate administrative commands or upload malicious firmware/configuration. No memory corruption or code injection is required; the attacker simply uses the authenticated session to perform privileged actions (e.g., altering firewall rules, enabling remote access, or exfiltrating data). The CVSS scope change (S:C) indicates the impact extends beyond the CGI component, likely to the device's operating system.

4. Post-Exploitation Impact: Full device compromise: the attacker can modify network configurations, intercept or redirect traffic, install persistent backdoors, or pivot into the internal network. With availability impact (A:H), they can also render the device inoperable. Given the 10.0 score, the consequences are severe.

Impact Assessment

• Confidentiality (C:H): Attackers can access sensitive device configurations, credentials, and network traffic.
• Integrity (I:H): Attackers can alter firmware, routing tables, firewall rules, and other critical settings.
• Availability (A:H): Attackers can disable the device or disrupt network connectivity.
• Scope (S:C): The vulnerability in the CGI component affects other components, potentially the entire device and connected network.
• Blast Radius: Any Netcore NR268 router with firmware 1.7.121109 exposed to untrusted networks is at risk. SOHO routers are often internet-facing, making mass exploitation feasible. Successful exploitation can lead to full network takeover, data theft, or use in botnets.

Detection Guidance

Sigma Rule

title: Netcore NR268 Authentication Bypass Attempt
id: 8f3c2e1a-4b5d-4c7e-9f0a-1b2c3d4e5f6a
status: experimental
description: Detects HTTP requests targeting the CGI authentication bypass in Netcore NR268 (CVE-2026-108907)
author: Threat Intelligence Team
date: 2026-01-15
logsource:
  category: webserver
  product: netcore
detection:
  selection:
    cs-method: 'GET'
    cs-uri-stem|contains: '/cgi-bin/'
    cs-uri-query|contains: 'user_ok'
  condition: selection
falsepositives:
  - Legitimate administrative access (rare)
level: critical
tags:
  - attack.initial_access
  - attack.t1190
  - cve.2026.108907

YARA Rule

rule CVE_2026_108907_Netcore_NR268_Auth_Bypass
{
    meta:
        description = "Detects exploitation attempts for CVE-2026-108907 in Netcore NR268 firmware"
        author = "Threat Intelligence Team"
        date = "2026-01-15"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-108907"
        hash = "unknown"
    strings:
        $s1 = "user_ok" ascii wide nocase
        $s2 = "NR268" ascii wide nocase
        $s3 = "1.7.121109" ascii wide nocase
        $cgi = "/cgi-bin/" ascii wide nocase
    condition:
        any of ($s*) and $cgi
}

Suricata IDS Rule

alert http any any -> any any (msg:"CVE-2026-108907 Netcore NR268 Authentication Bypass Attempt"; flow:to_server,established; content:"/cgi-bin/"; http_uri; content:"user_ok"; http_uri; nocase; reference:cve,2026-108907; reference:url,nvd.nist.gov/vuln/detail/CVE-2026-108907; classtype:attempted-admin; sid:10000001; rev:1;)

Elastic Detection

network where
  http.request.method == "GET" and
  stringContains(http.request.uri, "/cgi-bin/") and
  stringContains(http.request.uri, "user_ok")

Splunk SPL Query

index=web OR index=proxy
| search (uri_path="/cgi-bin/*" OR uri="*/cgi-bin/*") (uri_query="*user_ok*" OR uri="*user_ok*")
| stats count by src_ip, dest_ip, uri, status
| where status >= 200 AND status < 300

Wazuh OSSEC Rule

<group name="netcore,cve-2026-108907,">
  <rule id="100001" level="12">
    <decoded_as>web-accesslog</decoded_as>
    <match>user_ok</match>
    <match>/cgi-bin/</match>
    <description>CVE-2026-108907: Netcore NR268 authentication bypass attempt detected</description>
    <mitre>
      <id>T1190</id>
    </mitre>
    <group>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 management access from the WAN interface; restrict administrative access to a trusted management VLAN or VPN.
   • Place the device behind a firewall and block inbound access to HTTP/HTTPS management ports from untrusted networks.
   • If remote management is necessary, use IP allowlisting to permit only known trusted sources.
   • Monitor for anomalous requests to /cgi-bin/ scripts containing user_ok in the URI path or query string.
   • Consider replacing the device with a supported alternative if the vendor remains unresponsive.

2. Patch/Upgrade Steps:

   • No vendor patch is available. Contact Netcore support directly and request a security update.
   • Monitor the Netcore website and NVD for firmware updates addressing CVE-2026-108907.
   • If a patched firmware version is released, apply it immediately after testing in a non-production environment.

3. Long-term Hardening:

   • Implement network segmentation to isolate IoT/embedded devices from critical assets.
   • Enforce strong authentication mechanisms (e.g., multi-factor) on all management interfaces where supported.
   • Conduct regular vulnerability scanning and firmware audits for all network devices.
   • Adopt a policy of procuring devices from vendors with a proven security response track record.

References

1. NVD – CVE-2026-108907: https://nvd.nist.gov/vuln/detail/CVE-2026-108907
2. MITRE CWE-287 – Improper Authentication: https://cwe.mitre.org/data/definitions/287.html
3. FIRST EPSS – Not yet scored (as of report date)
4. CISA KEV Catalog – Not listed (as of report date)
5. Netcore Official Website – Monitor for security advisories: https://www.netcore.com (vendor did not respond to disclosure)