CVE-2026-51756Network attack vector

Unauthenticated firmware flashing via MQTT message

Published Sep 1, 2026 · Updated Sep 1, 2026

Incorrect access control in TOTOLINK T6 4.1.5cu.748_B20211015 allows remote attackers to start firmware flashing via MQTT. The cs_broker component accepts an unauthenticated message naming meshSlaveUpgfw and invokes that function with attacker-supplied Flags, without enforcing access control. The action uses an existing upgrade file; public evidence does not show that attackers can upload arbitrary firmware through this flaw.

CVSS severity5.9
Medium
EPSS probability0.34%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Incorrect access control in TOTOLINK T6 4.1.5cu.748_B20211015 allows remote attackers to start firmware flashing via MQTT. The cs_broker component accepts an unauthenticated message naming meshSlaveUpgfw and invokes that function with attacker-supplied Flags, without enforcing access control. The action uses an existing upgrade file; public evidence does not show that attackers can upload arbitrary firmware through this flaw.

The record

CVE
CVE-2026-51756
Published
Sep 1, 2026
Updated
Sep 1, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-284, T1210
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 1, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 1, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

5.9CISA-ADPCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-284Improper Access Control
T1210Exploitation of Remote Services

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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