CVE-2026-51757Network attack vector

Unauthenticated firmware flashing via crafted MQTT message

Published Sep 1, 2026 · Updated Sep 2, 2026

Incorrect access control in TOTOLINK T6 4.1.5cu.748_B20211015 allows remote attackers to trigger slave firmware updates via MQTT. The cs_broker component accepts a crafted message naming meshSlaveUpdate and forwards its Flags, serverIp, cloudUpg, and userdata_upg fields without authentication. Network access to the MQTT broker is sufficient to start a firmware download or flash workflow on a mesh slave, altering device firmware state.

CVSS severityUnavailable
Unscored
EPSS probability0.44%
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 trigger slave firmware updates via MQTT. The cs_broker component accepts a crafted message naming meshSlaveUpdate and forwards its Flags, serverIp, cloudUpg, and userdata_upg fields without authentication. Network access to the MQTT broker is sufficient to start a firmware download or flash workflow on a mesh slave, altering device firmware state.

The record

CVE
CVE-2026-51757
Published
Sep 1, 2026
Updated
Sep 2, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
T1495
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 1, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 2, 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

No CVSS assessment is available in this record.

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.

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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

T1495Firmware Corruption

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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