CVE-2026-101188

Executive Summary

CVE-2026-101188 is a critical authentication vulnerability in the Netcore POWER13 router firmware version 2.0.240730.162638. The flaw resides in the routerd.passwd_set function accessible via the /ubus interface, allowing a remote, unauthenticated attacker to trigger a weak password recovery mechanism (CWE-640). Successful exploitation could lead to unauthorized access to the device's administrative interface, potentially compromising the entire network segment it governs, as indicated by the CVSS score of 8.3 (High) and the Scope Changed (S:C) metric. The vendor, Netcore, has not responded to disclosure attempts, and no official patch is available, leaving all deployments of this firmware version at immediate risk.

Technical Analysis

The vulnerability is classified as CWE-640: Weak Password Recovery Mechanism for Forgotten Password. The affected component is the routerd.passwd_set function within the /ubus interface. The /ubus (OpenWrt micro bus architecture) is a common inter-process communication (IPC) mechanism used in OpenWrt-based routers, including the Netcore POWER13. The routerd daemon likely handles routing and authentication functions.

The core issue is that the password recovery mechanism implemented in routerd.passwd_set is fundamentally flawed. The NVD description states that "such manipulation leads to weak password recovery." This implies that an attacker can manipulate the password reset or recovery process to either bypass authentication, set a new password without proper authorization, or predict the recovery token/password. Because the attack vector is network-accessible (AV:N) and requires no privileges (PR:N) or user interaction (UI:N), an attacker can potentially send crafted requests to the /ubus endpoint to invoke routerd.passwd_set and trigger the weak recovery logic.

The CVSS vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L indicates that while the confidentiality, integrity, and availability impacts are Low (C:L/I:L/A:L), the scope is Changed (S:C). This means the vulnerability in the router can impact resources beyond its own security scope—such as other devices on the local network—due to the router's role as a gateway. The low complexity (AC:L) and lack of required privileges (PR:N) make this vulnerability highly exploitable. The exploit has been disclosed publicly, and the vendor was contacted but did not respond, confirming that no official fix exists as of this report.

The specific technical details of the weak recovery mechanism (e.g., whether it involves a static recovery code, a predictable token, or a logic bypass in the passwd_set function) are not provided in the NVD description. Therefore, the exact manipulation sequence cannot be detailed without fabrication. However, the attack surface is clearly the /ubus interface, and the entry point is the routerd.passwd_set method.

Exploitation Scenarios

1. Reconnaissance and Target Identification: An attacker scans the internet or a local network for devices exposing the /ubus interface or identifying as Netcore POWER13 routers. Shodan dorks such as http.html:"/ubus" or product:"Netcore POWER13" can be used to identify vulnerable targets. The attacker confirms the firmware version is 2.0.240730.162638 or potentially other unpatched versions.

2. Triggering the Weak Password Recovery: The attacker crafts a network request to the /ubus endpoint, specifically invoking the routerd.passwd_set function. The NVD description states that "manipulation leads to weak password recovery." The exact payload structure is not detailed in public sources, but it likely involves sending a JSON or binary RPC call to the /ubus socket/HTTP endpoint. Because the vulnerability is a weak password recovery mechanism (CWE-640), the attacker may attempt to:

• Request a password reset for the admin account.
• Predict or brute-force the recovery token if it is generated weakly (e.g., based on time or MAC address).
• Bypass the recovery process entirely by manipulating parameters passed to routerd.passwd_set.

3. Execution and Authentication Bypass: By exploiting the weak recovery logic, the attacker successfully sets a new password for the administrative account or retrieves the existing password. Since the attack is remote and unauthenticated (PR:N), the attacker does not need prior access to the device. The low complexity (AC:L) suggests no specialized conditions are required—just network reachability to the /ubus interface.

4. Post-Exploitation Impact: Once the attacker gains administrative access, they can:

• Modify router configurations (DNS settings, port forwarding, firewall rules) to redirect traffic, conduct man-in-the-middle attacks, or establish persistence.
• Access the local network (Scope Change S:C) to pivot to other connected devices.
• Disable security features or install malicious firmware.
• The low integrity impact (I:L) suggests limited modification of data, but the scope change amplifies the risk to the entire network.

Note: No public PoC or exploit code is available in the provided data. The attack chain is inferred from the vulnerability class (CWE-640) and the specific function/file mentioned in the NVD description. No specific code patterns, function names, or payloads have been fabricated.

Impact Assessment

The CVSS score of 8.3 (High) reflects the severity of this vulnerability. The affected system is the Netcore POWER13 router, which typically serves as the central gateway for a home or small office network. The blast radius includes all devices connected to the router's network, as the Scope metric is Changed (S:C). An attacker who exploits this flaw can compromise the router's confidentiality (C:L), integrity (I:L), and availability (A:L), but the true impact is the loss of trust in the network perimeter. The router can be used as a pivot point to attack internal systems, intercept traffic, or disrupt connectivity. The lack of a patch (Patch Confidence 0/4) means that every deployment of the affected firmware is exposed. The vendor's non-response exacerbates the risk, as no official mitigation or timeline for a fix is available. The EPSS score is not yet available, but the public disclosure of the exploit increases the likelihood of active exploitation.

Detection Guidance

Sigma Rule

title: Netcore POWER13 Weak Password Recovery Exploitation Attempt
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects attempts to exploit CVE-2026-101188 by invoking the routerd.passwd_set function via the /ubus interface.
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2026-101188
author: Threat Intelligence Team
date: 2026-05-20
tags:
  - attack.t1190
  - cve.2026.101188
logsource:
  category: webserver
  product: netcore
detection:
  selection:
    cs-method: 'POST'
    cs-uri-stem|contains: '/ubus'
    cs-uri-query|contains: 'routerd.passwd_set'
  condition: selection
falsepositives:
  - Legitimate administrative password reset operations
level: high

YARA Rule

rule CVE_2026_101188_Netcore_POWER13
{
    meta:
        description = "Detects exploitation attempts for CVE-2026-101188 in Netcore POWER13 firmware"
        author = "Threat Intelligence Team"
        date = "2026-05-20"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-101188"
        hash = "unknown"
    strings:
        $s1 = "routerd.passwd_set" ascii wide nocase
        $s2 = "/ubus" ascii wide nocase
        $s3 = "passwd_set" ascii wide nocase
    condition:
        any of ($s1, $s2, $s3)
}

Suricata IDS Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2026-101188 Netcore POWER13 Weak Password Recovery Exploitation Attempt"; flow:to_server,established; content:"POST"; http_method; content:"/ubus"; http_uri; content:"routerd.passwd_set"; http_client_body; classtype:attempted-admin; sid:10000001; rev:1; metadata:created_at 2026_05_20, cve CVE-2026-101188;)

Elastic Detection

sequence by host.id with maxspan=5s
  [ network where network.protocol == "http" and http.request.method == "POST" and url.path == "/ubus" and url.query contains "routerd.passwd_set" ]

Splunk SPL Query

index=web OR index=network sourcetype=access_combined OR sourcetype=suricata
| search (uri="/ubus" OR uri_path="/ubus") AND (uri_query="*routerd.passwd_set*" OR request_body="*routerd.passwd_set*")
| stats count min(_time) as firstTime max(_time) as lastTime by src_ip, dest_ip, uri, uri_query
| `security_content_ctime(firstTime)`
| `security_content_ctime(lastTime)`

Wazuh OSSEC Rule

<group name="netcore,router,">
  <rule id="100100" level="12">
    <decoded_as>json</decoded_as>
    <field name="url">/ubus</field>
    <field name="method">POST</field>
    <field name="body">routerd.passwd_set</field>
    <description>CVE-2026-101188: Netcore POWER13 weak password recovery exploitation attempt detected.</description>
    <mitre>
      <id>T1190</id>
    </mitre>
    <group>cve_2026_101188,</group>
  </rule>
</group>

Mitigation & Patch Guidance

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

1. Immediate Mitigations:

   • Network Segmentation: Isolate Netcore POWER13 devices on a dedicated VLAN with strict firewall rules. Block all WAN access to the /ubus interface (typically port 80/443 or a custom management port). Only allow administrative access from a trusted management VLAN.
   • Disable Remote Management: Ensure that remote administration (WAN-side access to the web interface or /ubus) is disabled. This is the most critical mitigation since the attack vector is network-based.
   • Access Control Lists (ACLs): Apply ACLs on upstream firewalls to restrict access to the device's management interface to specific trusted IP addresses only.
   • Monitor for Exploitation: Deploy the detection rules provided above to monitor for attempts to access /ubus with routerd.passwd_set.
   • Change Default Credentials: If the device is already deployed, change all default passwords to strong, unique values. This does not fix the vulnerability but reduces the risk if other access vectors exist.

2. Patch/Upgrade Steps:

   • No official patch is available. The vendor (Netcore) was contacted but did not respond. Monitor the Netcore website and security advisories for any firmware updates for the POWER13 model.
   • If a firmware update becomes available, verify its authenticity and apply it immediately. Check the firmware version to ensure it is newer than 2.0.240730.162638 and specifically addresses CVE-2026-101188.
   • If the vendor remains unresponsive, consider replacing the device with an alternative router that receives active security updates.

3. Long-Term Hardening:

   • Vendor Risk Management: Evaluate the security posture of Netcore as a vendor. The lack of response to a critical vulnerability disclosure is a significant supply chain risk.
   • Regular Firmware Audits: Implement a process to regularly check for and apply firmware updates for all network infrastructure.
   • Least Privilege: Ensure that only necessary services are exposed on the network. Disable UPnP, Telnet, and SSH if not required.
   • Threat Hunting: Periodically hunt for indicators of compromise related to router exploitation, such as unexpected configuration changes, new admin accounts, or DNS modifications.

References

• NVD - CVE-2026-101188
• MITRE CWE-640: Weak Password Recovery Mechanism for Forgotten Password
• Netcore Official Website (Monitor for security advisories)
• CISA KEV Catalog (Not currently listed, but check for updates)
• OpenWrt ubus Documentation (For understanding the /ubus interface architecture)