CVE-2026-51756
Received Received - Intake

Incorrect Access Control in TOTOLINK T6 Firmware Upgrade

Publication date: 2026-09-01

Last updated on: 2026-09-01

Assigner: MITRE

Description
Incorrect access control in the meshSlaveUpgfw function of TOTOLINK T6 4.1.5cu.748_B20211015 allows unauthenticated attackers to start firmware flashing using existing upgrade files via sending a crafted MQTT message to the cs_broker component.

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Meta Information

Published
2026-09-01
Last Modified
2026-09-01
Generated
2026-09-01
AI Q&A
2026-09-01
EPSS Evaluated
N/A
NVD
CVE-2026-51756
EUVD
EUVD-2026-69201

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
totolink t6 4.1.5cu.748_b20211015

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Exploitability

CWE
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KEV
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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability is an incorrect access control issue in the meshSlaveUpgfw function of TOTOLINK T6 firmware version 4.1.5cu.748_B20211015. It allows unauthenticated attackers to initiate firmware flashing by sending a specially crafted MQTT message to the cs_broker component using existing upgrade files.

Detection Guidance

Detecting this vulnerability requires monitoring for unauthorized MQTT messages targeting the cs_broker component. Check network traffic for unexpected MQTT packets sent to port 1883 or 8883. Inspect logs for firmware flashing attempts without authentication. Use tcpdump or Wireshark to capture MQTT traffic and filter for messages containing 'meshSlaveUpgfw' or 'firmware flashing' keywords.

Impact Analysis

An attacker could exploit this to flash malicious firmware on your device without authentication. This could lead to unauthorized control of the device, data theft, or turning it into a botnet participant. Users should update firmware immediately if available.

Mitigation Strategies

Immediately restrict access to the MQTT broker by blocking external connections to ports 1883 and 8883. Update the TOTOLINK T6 firmware to the latest version if available. Disable unnecessary MQTT services if not required. Monitor for unauthorized firmware flashing attempts and restrict write permissions to upgrade files.

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