CVE-2026-108930

Executive Summary

CVE-2026-108930 is an information disclosure vulnerability in Netcore NR268 firmware version 1.7.121109, located in the DDNS handler component. The flaw resides in the ddns_wan_list_show function within ddns_wan_list_show.cgi, where manipulation of the user_idN/passwordN arguments exposes sensitive credential data. The vulnerability is remotely exploitable and has been publicly disclosed, but it requires high privileges (PR:H) to trigger, yielding a low CVSS score of 2.7; the vendor has not responded to disclosure attempts, leaving all devices unpatched.

Technical Analysis

The affected product is the Netcore NR268 router, a small-office/home-office (SOHO) networking device. The vulnerability is located in the DDNS (Dynamic DNS) handler component, specifically the CGI script ddns_wan_list_show.cgi. The ddns_wan_list_show function is responsible for presenting the list of configured WAN DDNS entries. The NVD description states that "manipulation of the argument user_idN/passwordN leads to information disclosure." This indicates that the script processes parameters named user_idN and passwordN (where N likely denotes an index for multiple DDNS entries) and improperly exposes sensitive information—most plausibly the stored DDNS credentials (username and password) for the WAN interface.

The vulnerability class is CWE-200: Exposure of Sensitive Information to an Unauthorized Actor. The attack vector is network-accessible (AV:N), and no user interaction is required (UI:N). However, the attacker must possess high privileges (PR:H), meaning authentication as an administrative user or equivalent is necessary to reach the vulnerable CGI script. The CVSS subscores reflect a confidentiality-only impact (C:L) with no integrity or availability impact.

The exact mechanism of information disclosure is not detailed in the NVD description. It is not specified whether the script echoes credentials in the HTTP response, allows arbitrary users to retrieve credentials for DDNS entries they should not access, or performs insufficient access control on the user_idN/passwordN parameters. No code-level details are available, and no patch or vendor analysis exists. The vulnerability is confirmed to be remotely exploitable and has a public exploit, though no PoC or exploit code is included in the provided data.

The attack surface is the router's web management interface, specifically the CGI endpoint for DDNS list display. An attacker with administrative access (or who has compromised an administrative session) can send a crafted HTTP request to ddns_wan_list_show.cgi with manipulated user_idN and passwordN parameters to retrieve sensitive DDNS credentials.

Exploitation Scenarios

Given the sparse technical detail in the NVD description, the following exploitation chain is inferred at the vulnerability-class level. No public PoC is available in the provided data; however, the description states "the exploit has been disclosed to the public and may be used."

1. Reconnaissance / Target Identification: An attacker identifies Netcore NR268 routers exposed to the internet or within a targeted network. Shodan dorks such as product:"Netcore NR268" or http.html:"ddns_wan_list_show" can be used to locate devices with the DDNS management interface accessible. The attacker must then obtain valid administrative credentials (high privileges required) through prior compromise, default credentials, or social engineering.

2. Triggering the Flaw: With administrative access, the attacker crafts an HTTP request to the CGI endpoint ddns_wan_list_show.cgi, invoking the ddns_wan_list_show function. The request includes manipulated user_idN and passwordN arguments. The exact manipulation is not described in the NVD data, but the vulnerability class (CWE-200) suggests that the script fails to properly restrict access to the credential fields, allowing the attacker to retrieve DDNS usernames and passwords that are stored in the router's configuration.

3. Payload/Execution Method: At the vulnerability-class level, the attack is an HTTP GET or POST request to the CGI script with parameters that cause the script to return sensitive information in the response. No specific injection payload is provided in the available data. The exploit likely relies on parameter tampering to bypass intended access controls or to cause the script to output credential data directly.

4. Post-Exploitation Impact: Successful exploitation discloses DDNS service credentials (username and password) for one or more WAN interfaces. These credentials could be leveraged for lateral movement, to hijack the DDNS account, to redirect domain names, or to gain further access to other services tied to the same credentials. The confidentiality impact is low per CVSS (C:L), but the disclosed credentials may have broader security implications if reused.

Impact Assessment

The CVSS v3.1 score is 2.7 (Low), with the vector CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:N/A:N. The attack is network-accessible (AV:N) with low complexity (AC:L), but requires high privileges (PR:H), meaning the attacker must already possess administrative access to the router. There is no user interaction (UI:N), and the scope is unchanged (S:U). The only impacted security property is confidentiality, and the impact is low (C:L), reflecting that only some DDNS credential information may be exposed. Integrity and availability are not affected.

Business impact is limited to organizations or individuals using the Netcore NR268 router with DDNS configured. The exposure of DDNS credentials could allow an attacker to hijack the dynamic DNS account, potentially redirecting domain traffic or disrupting remote access services. However, because high privileges are required, the vulnerability is most relevant in post-authentication scenarios or when administrative credentials are weak or default. The blast radius is confined to the affected router and the DDNS accounts configured on it. No server-side or cloud infrastructure is directly impacted.

The EPSS score is not yet available from FIRST.org. CISA KEV status is NO. No public PoC, exploit code, or Nuclei template is available in the provided data, though the description states the exploit has been publicly disclosed. There is no vendor fix, workaround, or affected version list beyond the specific firmware version 1.7.121109.

Detection Guidance

Sigma Rule

title: Netcore NR268 DDNS Credential Information Disclosure Attempt
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects HTTP requests to the DDNS handler CGI script with manipulated user_idN/passwordN parameters indicative of CVE-2026-108930.
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2026-108930
author: valtersit.com
date: 2025-04-09
tags:
  - attack.t1190
  - cve.2026.108930
logsource:
  category: webserver
  product: netcore
detection:
  selection_uri:
    cs-uri-stem|endswith: '/ddns_wan_list_show.cgi'
  selection_params:
    cs-uri-query|contains:
      - 'user_id'
      - 'password'
  condition: selection_uri and selection_params
falsepositives:
  - Legitimate administrative DDNS configuration retrieval
level: medium

YARA Rule

rule CVE_2026_108930_Netcore_DDNS_InfoDisclosure
{
    meta:
        description = "Detects Netcore NR268 DDNS handler CGI script vulnerable to information disclosure CVE-2026-108930"
        author = "valtersit.com"
        date = "2025-04-09"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-108930"
        severity = "low"
    strings:
        $cgi = "ddns_wan_list_show.cgi"
        $func = "ddns_wan_list_show"
        $param1 = "user_id"
        $param2 = "password"
    condition:
        uint16(0) == 0x213C or uint16(0) == 0x3C21 or true
        and any of ($cgi, $func)
        and all of ($param1, $param2)
}

Suricata IDS Rule

alert http any any -> any any (msg:"CVE-2026-108930 Netcore NR268 DDNS Credential Information Disclosure Attempt"; flow:to_server,established; http.uri; content:"/ddns_wan_list_show.cgi"; http.uri; content:"user_id"; http.uri; content:"password"; classtype:attempted-recon; reference:cve,2026-108930; reference:url,nvd.nist.gov/vuln/detail/CVE-2026-108930; sid:2026108930; rev:1;)

Elastic Detection

network where
  url.path : "/ddns_wan_list_show.cgi" and
  url.query : ("*user_id*" or "*password*")

Splunk SPL Query

index=web sourcetype=access_combined
| search uri_path="/ddns_wan_list_show.cgi" (uri_query="*user_id*" OR uri_query="*password*")
| stats count min(_time) as first_seen max(_time) as last_seen by src_ip, uri_path, uri_query, status
| where count > 0
| convert ctime(first_seen) ctime(last_seen)

Wazuh OSSEC Rule

<group name="netcore,web,cve-2026-108930,">
  <rule id="2026108" level="6">
    <if_sid>31100</if_sid>
    <id>^/ddns_wan_list_show\.cgi</id>
    <match>user_id|password</match>
    <description>CVE-2026-108930: Netcore NR268 DDNS credential information disclosure attempt detected</description>
    <mitre>
      <id>T1190</id>
    </mitre>
    <group>cve_2026_108930,attempted_recon,</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 router's web management interface to trusted internal networks only; do not expose the DDNS management CGI to the internet.
   • Enforce strong, unique administrative credentials and enable multi-factor authentication if supported.
   • Monitor HTTP logs for requests to ddns_wan_list_show.cgi with user_idN/passwordN parameters, as described in the detection guidance above.
   • Consider disabling DDNS if not required, reducing the attack surface.
   • Since the vendor did not respond, no official workaround exists. Isolate affected devices on a segmented VLAN with strict firewall rules.

2. Patch/Upgrade Steps:

   • No vendor patch is available. The vendor was contacted but did not respond.
   • Monitor the Netcore website and security advisories for any future firmware release addressing this vulnerability.
   • If a patched firmware becomes available, upgrade immediately following vendor instructions.
   • Until a patch exists, consider replacing the device with a supported alternative if the risk is unacceptable.

3. Long-Term Hardening:

   • Implement network segmentation to limit the blast radius of compromised routers.
   • Regularly audit router configurations for exposed credentials and unnecessary services.
   • Use a centralized logging and monitoring solution to detect anomalous access to management interfaces.
   • Enforce the principle of least privilege for administrative accounts.
   • Plan for hardware lifecycle management; unsupported or unresponsive vendors pose ongoing risk.

References

• NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-108930
• Netcore official website (vendor): https://www.netcore.com/ (no advisory published)
• CWE-200: https://cwe.mitre.org/data/definitions/200.html
• MITRE ATT&CK T1190: https://attack.mitre.org/techniques/T1190/
• No CISA KEV entry; no known threat actor campaigns or exploit-in-the-wild evidence available at this time.