CVE-2026-102762

Executive Summary

CVE-2026-102762 is a memory leak vulnerability in the Eclipse NetX Duo MQTT client that causes a denial-of-service condition. When the client processes a malformed PUBLISH message, it fails to release the network packet buffer back to the driver's receive pool. An unauthenticated remote attacker can send a small number of malformed PUBLISH messages to exhaust the receive pool, causing all inbound network traffic to stop until the device is rebooted. This affects any embedded device running the NetX Duo MQTT client in an unpatched state.

Technical Analysis

The vulnerability resides in the NetX Duo MQTT client implementation. According to the NVD description, the client "leaks the packet carrying a malformed PUBLISH message." Each malformed PUBLISH consumes one packet, or one chain of packets, from the network driver's receive pool without returning it. The root cause aligns with CWE-401 (Missing Release of Memory after Effective Lifetime), where allocated memory or buffer resources are not freed after processing. The attack surface is the MQTT protocol endpoint exposed by the client. The flaw is triggered when a PUBLISH message fails validation or parsing, and the code path handling the error condition fails to call the appropriate buffer release function. No specific function names, code lines, or internal APIs are provided in the advisory data; therefore, the exact implementation detail is not available. The impact is resource exhaustion: the receive pool is finite, and once depleted, the network driver cannot accept new inbound packets, effectively halting all network communication on the device. Recovery requires a reboot. The CVSS vector is estimated as AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H, reflecting a network-accessible, low-complexity, unauthenticated attack with high availability impact. No official CVSS score is assigned; the vector is inferred from the vulnerability class and impact.

Exploitation Scenarios

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

1. Reconnaissance/target identification: The attacker scans for devices exposing MQTT services, typically on TCP port 1883 or 8883. Shodan dorks such as "MQTT", port:1883, or port:8883 can identify candidate targets. Devices running NetX Duo MQTT client may be identified by banner grabbing or fingerprinting the MQTT CONNECT response.

2. Triggering the flaw: The attacker establishes a connection to the MQTT broker or directly to the client if it acts as a server (depending on deployment). The attacker sends a malformed PUBLISH message. The exact malformation is not specified in the advisory, but it must be a PUBLISH packet that the client's parser rejects or fails to process correctly. Upon processing, the client leaks the packet buffer instead of returning it to the receive pool.

3. Payload/execution method: The attacker repeats the malformed PUBLISH message. Each message leaks one packet or a chain of packets from the receive pool. The exact number required to exhaust the pool depends on the pool size, which is configuration-dependent. The NVD description states "a few dozen such messages" can exhaust the pool. No specific packet crafting details or byte sequences are provided; the attack is at the protocol level.

4. Post-exploitation impact: Once the receive pool is exhausted, the network driver cannot accept any new inbound packets. All inbound network traffic on the device stops. The device becomes unresponsive to network requests, including legitimate MQTT messages, management traffic, or other protocols sharing the same driver. The condition persists until the device is rebooted. This is a denial-of-service attack with no confidentiality or integrity impact.

Impact Assessment

The vulnerability allows an unauthenticated remote attacker to cause a complete denial of service on affected devices. The blast radius includes any embedded system running the NetX Duo MQTT client that is reachable over the network. Industrial control systems, IoT gateways, medical devices, and automotive components are potential targets. The CVSS vector AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H indicates a high availability impact, with no impact to confidentiality or integrity. The attack is low complexity and requires no privileges or user interaction. The business impact includes operational downtime, loss of telemetry, inability to control or monitor devices, and potential safety implications if the device is part of a critical process. Recovery requires physical or remote reboot, which may be disruptive. The EPSS score is not yet available, and the CVE is not in CISA KEV.

Detection Guidance

Sigma Rule

title: NetX Duo MQTT Malformed PUBLISH Memory Leak DoS
id: 8a4b3c2d-1e5f-4a7b-9c8d-0e1f2a3b4c5d
status: experimental
description: Detects repeated malformed MQTT PUBLISH messages that may trigger CVE-2026-102762 memory leak in NetX Duo MQTT client.
author: Valters IT
date: 2026-01-01
logsource:
  category: network_connection
  product: mqtt
detection:
  selection:
    event: "MQTT_PUBLISH"
    malformed: true
  condition: selection | count() by src_ip > 20 within 60 seconds
  timeframe: 60s
falsepositives:
  - Legitimate malformed packets due to network errors
level: high
tags:
  - attack.t1499
  - cve.2026.102762

YARA Rule

rule CVE_2026_102762_NetX_Duo_MQTT_Leak
{
    meta:
        description = "Detects malformed MQTT PUBLISH packets targeting NetX Duo MQTT client"
        author = "Valters IT"
        date = "2026-01-01"
        reference = "CVE-2026-102762"
        hash = "unknown"
    strings:
        $mqtt_publish = { 30 } // MQTT PUBLISH packet type (0x30) followed by variable length
        $mqtt_connect = { 10 } // MQTT CONNECT packet type
    condition:
        $mqtt_publish at 0 and #mqtt_publish > 20
}

Suricata IDS Rule

alert tcp any any -> any 1883 (msg:"CVE-2026-102762 NetX Duo MQTT Malformed PUBLISH Memory Leak Attempt"; flow:to_server,established; content:"|30|"; offset:0; depth:1; content:"|00|"; within:2; threshold: type both, track by_src, count 20, seconds 60; classtype:attempted-dos; sid:1000001; rev:1; reference:cve,2026-102762;)

Elastic Detection

sequence by source.ip with maxspan=1m
  [network where network.protocol == "mqtt" and mqtt.packet_type == "PUBLISH" and mqtt.malformed == true] with runs=20

Splunk SPL Query

index=network sourcetype=mqtt
| search packet_type=PUBLISH malformed=true
| stats count by src_ip
| where count > 20
| table src_ip, count

Wazuh OSSEC Rule

<group name="mqtt,">
  <rule id="100001" level="10">
    <decoded_as>json</decoded_as>
    <field name="protocol">mqtt</field>
    <field name="packet_type">PUBLISH</field>
    <field name="malformed">true</field>
    <description>CVE-2026-102762: Malformed MQTT PUBLISH message detected - potential memory leak DoS</description>
    <mitre>
      <id>T1499</id>
    </mitre>
    <group>dos,</group>
  </rule>
</group>

Mitigation & Patch Guidance

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

1. Immediate mitigations:

• Disable MQTT if not required. If MQTT is required, restrict network access to the MQTT client using firewall rules, ACLs, or network segmentation to trusted IP addresses only.
• Implement rate limiting on MQTT connections to reduce the number of malformed PUBLISH messages that can be delivered.
• Monitor device memory and receive pool usage for signs of exhaustion; set up alerts for sudden increases in packet buffer utilization.
• Where possible, enable automatic watchdog reboot if the device becomes unresponsive.

2. Patch/upgrade steps:

• No official patch is available. Check Eclipse ThreadX / NetX Duo repositories and vendor advisories for updates. Apply updates as soon as they become available.
• If using a commercial embedded OS that incorporates NetX Duo, contact the vendor for a patched build.

3. Long-term hardening:

• Replace the NetX Duo MQTT client with an alternative MQTT implementation that has a proven record of memory safety, or isolate MQTT traffic in a demilitarized zone (DMZ).
• Conduct code reviews and fuzz testing on MQTT parsing code to identify similar resource management issues.
• Adopt secure coding standards that enforce strict validation and release of network buffers on all error paths.
• Implement resource quotas and recovery mechanisms to prevent single-point resource exhaustion.

References

• NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-102762
• Eclipse ThreadX: https://github.com/eclipse-threadx/netxduo
• CWE-401: https://cwe.mitre.org/data/definitions/401.html
• MITRE ATT&CK T1499: https://attack.mitre.org/techniques/T1499/
• No known threat actor campaigns or exploit-in-the-wild evidence at this time.