CVE-2026-77056 in black_debian_images
Summary
by MITRE • 10/26/2026
boneIO black_debian_images ships with a Mosquitto MQTT broker that uses the same default credentials on all devices. These credentials are publicly documented on github, and there is no indication in the instructions to change them. A remote attacker can use them to gain full read and write access to the broker, allowing control of connected relays, blinds, and gates, and injection of fake entities into a linked Home Assistant installation.
This issue was fixed in version 1.6.0 of the image: MQTT passwords are generated per device at first boot. Devices upgraded from earlier versions keep their existing broker credentials; from boneio 1.6.0 the web panel reports credentials that are still the published defaults, and the owner has to change them.
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Analysis
by VulDB Data Team • 10/26/2026
The vulnerability identified in boneIO black_debian_images stems from a critical failure in default credential management for the Mosquitto MQTT broker embedded within the system. This flaw represents a classic instance of hardcoded or static credentials that remain unchanged across all deployed devices, creating a uniform attack surface. The specific technical deficiency lies in the absence of unique per-device authentication tokens during initial provisioning. Instead, every unit ships with identical username and password combinations for its message queue telemetry transport service. These default credentials are not only present on the device but are also publicly documented on GitHub repositories associated with the project. This transparency effectively hands remote attackers a ready-made key to the system without requiring any exploitation of complex code logic or buffer overflows, relying instead on social engineering and reconnaissance rather than technical sophistication.
From an operational perspective, this vulnerability allows for unauthorized full read and write access to the MQTT broker. Since Mosquitto serves as the central nervous system for home automation devices in this architecture, gaining control of it equates to controlling the physical environment managed by the software. An attacker can issue commands to toggle connected relays, operate motorized blinds, or open and close gates remotely. Beyond direct hardware manipulation, the vulnerability enables data exfiltration through reading sensor states and historical logs. Furthermore, an adversary can inject fake entities into a linked Home Assistant installation. This capability allows for sophisticated attacks such as spoofing sensor readings to trigger false alarms, disrupting automated routines based on incorrect environmental data, or creating phantom devices that could be used for further lateral movement within the home network if other services trust MQTT messages blindly.
The remediation strategy implemented in version 1.6.0 of the image addresses this by generating unique passwords per device during the first boot process. This shift from static to dynamic credential generation significantly raises the barrier for attackers, as they can no longer rely on a single set of credentials to compromise multiple devices or even gain initial access without prior reconnaissance specific to each target. However, the mitigation is not entirely seamless due to backward compatibility concerns. Devices upgraded from earlier versions retain their existing broker credentials rather than being forced into new ones during the upgrade process. This creates a persistent risk for legacy installations that have not been manually secured. Additionally, there is a notable usability and security gap in version 1.6.0 where the web panel continues to report the published default credentials even after they may have been changed or if the device has not yet generated its unique token. This discrepancy can mislead owners into believing their system is secure when it might still be vulnerable, particularly for those who upgrade without reading detailed release notes regarding credential management.
To fully mitigate this risk, users of boneIO systems must take proactive steps beyond relying on automatic updates. For devices running versions prior to 1.6.0 or upgraded instances that retain old credentials, the owner should manually change the MQTT broker username and password through the available configuration interfaces if supported, or by directly modifying the Mosquitto authentication files within the Debian image environment. It is crucial to ensure that strong, unique passwords are used for each device rather than reusing common defaults. Network-level mitigations such as placing the MQTT broker on a segregated VLAN with strict firewall rules limiting access to only trusted IP addresses can provide defense in depth. Furthermore, enabling TLS encryption for MQTT connections prevents eavesdropping and man-in-the-middle attacks that could capture credentials if they are transmitted over unencrypted channels during initial setup or reconfiguration.
This vulnerability aligns closely with CWE-798: Use of Hard-coded Credentials, which describes the use of static authentication parameters in software code or configuration files. It also relates to CWE-256: Unprotected Storage of Credentials, as the default passwords are stored and transmitted without adequate protection mechanisms like hashing or encryption during initial deployment phases where they might be exposed via network sniffing if TLS is not enforced by default. In terms of the MITRE ATT&CK framework, this scenario facilitates Initial Access through Valid Accounts (T1078) and potentially Persistence if attackers modify configuration files to maintain access after reboots. The ability to inject fake entities into Home Assistant also touches upon Supply Chain Compromise concepts where trusted data sources are manipulated to deceive downstream systems. Organizations deploying these devices should treat the MQTT broker as a high-value target requiring strict authentication policies, regular audits of default credential usage, and immediate patching or manual remediation for any device that has not undergone the secure first-boot process introduced in version 1.6.0.