EUVD-2026-69378
GHSA-f853-c4vj-vrrq
Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Network-accessible MQTT endpoint requires no credentials; impact is write-only QoS policy modification with no confidentiality exposure or direct availability loss.
Primary rating from Vendor (mitre).
CVSS VectorVendor: mitre
Lifecycle Timeline
4DescriptionCVE.org
Incorrect access control in the setElinkQosConfig function of TOTOLINK T6 4.1.5cu.748_B20211015 allows unauthenticated attackers to modify privileged QoS policy on the master device via sending a crafted MQTT message to the cs_broker component.
AnalysisAI
Unauthenticated modification of privileged QoS policy is possible on TOTOLINK T6 routers running firmware 4.1.5cu.748_B20211015 via the setElinkQosConfig function, reachable by sending a crafted MQTT message to the cs_broker component without any credentials. The access control check is entirely absent for this function, exposing a privileged network management operation to any attacker who can reach the MQTT broker over the network. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | The cs_broker MQTT broker port must be reachable from the attacker's network; if cs_broker binds only to the LAN interface (typical for SOHO routers in default configuration), exploitation is constrained to attackers with local network access. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 3.1 vector (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N) yields a score of 7.5 High, reflecting a trivially exploitable network path with no authentication required and no technical complexity, but bounded impact - confined to integrity (QoS policy overwrite) with no confidentiality or direct availability consequence at the CVSS level. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | No vendor-released patch has been identified at the time of analysis. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, identify all TOTOLINK T6 deployments in your environment and audit firewall rules to determine if MQTT broker ports (1883, 8883) are exposed to untrusted networks; if exposed, implement immediate network segmentation to restrict MQTT access. …
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Same weakness CWE-284 – Improper Access Control
View allSame technique Authentication Bypass
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External POC / Exploit Code
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