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.
Published: 2026-09-01
Score: 5.9 Medium
EPSS: < 1% Very Low
KEV: No
Impact: Remote Code Execution via Firmware Flashing
Action: Immediate Patch
AI Analysis

Impact

The vulnerability resides in the meshSlaveUpgfw function of TOTOLINK T6 firmware version 4.1.5cu.748_B20211015. It allows an unauthenticated attacker to craft an MQTT message to the cs_broker component, triggering the device to start flashing firmware using existing upgrade files. Because flashing firmware writes arbitrary code to the device’s storage, this flaw can effectively result in Remote Code Execution, granting full control over the affected router.

Affected Systems

This issue affects TOTOLINK brand routers running firmware version 4.1.5cu.748_B20211015. No other products are listed.

Risk and Exploitability

The CVSS score is 5.9, and EPSS data is not available, and the vulnerability is not listed in CISA KEV. The attack vector is inferred to be network‑based via MQTT connections to the cs_broker component, and it requires no authentication. Given the lack of public exploitation data, the likelihood remains uncertain, but the potential impact is severe enough to warrant urgent attention.

Generated by OpenCVE AI on September 2, 2026 at 04:27 UTC.

Remediation

No vendor fix or workaround currently provided.

OpenCVE Recommended Actions

  • Update the device firmware to the latest patch released by TOTOLINK that removes the access control flaw.
  • Restrict or disable MQTT traffic to the cs_broker component to block forged update messages.
  • Implement network segmentation and monitoring to detect anomalous firmware upload attempts and block them.

Generated by OpenCVE AI on September 2, 2026 at 04:27 UTC.

Tracking

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Advisories

No advisories yet.

History

Wed, 02 Sep 2026 08:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Wed, 02 Sep 2026 04:45:00 +0000

Type Values Removed Values Added
Title Unauthorized Firmware Flashing via Crafted MQTT in TOTOLINK T6 Router

Wed, 02 Sep 2026 01:45:00 +0000

Type Values Removed Values Added
Title Unauthenticated Firmware Flashing via MQTT in TOTOLINK T6
Weaknesses CWE-269

Tue, 01 Sep 2026 22:00:00 +0000

Type Values Removed Values Added
Title Unauthenticated Firmware Flashing via MQTT in TOTOLINK T6
First Time appeared Totolink
Totolink t6
Weaknesses CWE-269
CWE-284
Vendors & Products Totolink
Totolink t6
Metrics cvssV3_1

{'score': 5.9, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N'}

Tue, 01 Sep 2026 14:00:00 +0000

Type Values Removed Values Added
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.
References

Subscriptions

Totolink T6
cve-icon MITRE

Status: PUBLISHED

Assigner: mitre

Published:

Updated: 2026-09-01T19:22:51.270Z

Reserved: 2026-06-08T00:00:00.000Z

Link: CVE-2026-51756

cve-icon Vulnrichment

Updated: 2026-09-01T19:21:13.430Z

cve-icon NVD

Status : Deferred

Published: 2026-09-01T14:17:36.150

Modified: 2026-09-01T21:00:36.830

Link: CVE-2026-51756

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-09-02T04:30:04Z

Weaknesses