CVE-2026-77060 in black_debian_images
Summary
by MITRE • 10/26/2026
boneIO black_debian_images stores the Mosquitto MQTT broker password file at /etc/mosquitto/passwd with world-readable permissions. Any local user can read the password hashes for all MQTT accounts and perform offline dictionary attacks.
This issue was fixed in version 1.6.0.
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Analysis
by VulDB Data Team • 10/26/2026
The vulnerability identified in boneIO black_debian_images involves an improper configuration of file system permissions for sensitive authentication data, specifically within the Mosquitto MQTT broker environment. The core technical flaw lies in the storage and access control settings applied to the password hash file located at /etc/mosquitto/passwd. In a properly secured Linux-based IoT or embedded device, files containing cryptographic hashes of user credentials must be restricted to root-only read permissions to prevent unauthorized disclosure. However, due to misconfiguration during image creation or deployment, this critical configuration file was assigned world-readable permissions. This means that any process running with the privileges of a standard local user on the system can open and read the contents of this file without requiring elevated access rights such as sudo or root credentials.
The operational impact of this vulnerability is significant because it facilitates unauthorized credential acquisition through offline attacks. Since MQTT brokers often handle sensitive telemetry data, control commands, and device status updates in IoT ecosystems, compromising the authentication mechanism undermines the entire security posture of the system. An attacker with local access to the device can extract all stored password hashes for every configured MQTT account. Once these hashes are obtained, they can be subjected to offline dictionary attacks or brute-force attempts using common tools like hashcat or John the Ripper. Unlike online attacks which may trigger rate-limiting mechanisms or intrusion detection alerts, offline cracking allows an attacker to attempt millions of guesses per second without being detected by the broker itself, potentially leading to full account compromise and subsequent remote control over connected devices if weak passwords are used.
From a classification perspective, this issue aligns with CWE-732: Incorrect Permission Assignment for Critical Resource, as it involves granting inappropriate access rights to a file containing sensitive information. It also relates to CWE-522: Insufficiently Protected Credentials, highlighting the failure to protect authentication data against unauthorized disclosure. In terms of adversary tactics, this vulnerability supports the ATT&CK technique T1003: OS Credential Dumping, specifically through local credential harvesting methods where an attacker extracts password hashes from configuration files or system databases on a compromised host. The ability to dump these credentials locally is often a precursor to lateral movement within a network if those same credentials are reused across multiple services or devices in the IoT environment.
Mitigation strategies for this vulnerability primarily involve correcting the file permissions immediately upon deployment and ensuring that build processes enforce strict security defaults. Administrators should execute chmod 600 /etc/mosquitto/passwd to restrict access to only the root user, who is typically the owner of the Mosquitto service process. Furthermore, organizations must ensure that their CI/CD pipelines or image building scripts include automated checks for file permission integrity before finalizing device images. Upgrading to version 1.6.0 resolves this issue by correcting these default permissions in the distribution package. For environments where upgrading is not immediately feasible, implementing mandatory access control systems such as SELinux or AppArmor can provide an additional layer of defense by restricting read access to specific system users regardless of traditional Unix file permission settings. Regular security audits and configuration management tools like Ansible or Puppet should be employed to continuously verify that critical files maintain their intended restrictive permissions over the lifecycle of the device.