CVE-2026-75166 in Firmware
Summary
by MITRE • 09/04/2026
Insecure Permission vulnerability in MBS-Solutions X-Serie Gateway firmware V6_00_05 allows the low-privileged service user to execute /usr/bin/tcpdump as root without a password. By leveraging the tcpdump -z option, an authenticated attacker can achieve arbitrary command execution.
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Analysis
by VulDB Data Team • 09/04/2026
The vulnerability identified in MBS-Solutions X-Series Gateway firmware version V6_00_05 represents a critical escalation of privilege rooted in insecure file permissions and improper configuration of system utilities. Specifically, the flaw allows any low-privileged service user to execute the binary located at /usr/bin/tcpdump with root-level privileges without requiring an authentication password. This misconfiguration effectively bypasses standard access control mechanisms that are designed to restrict powerful network diagnostic tools to administrative accounts only. The presence of such a permission setting indicates a failure in the principle of least privilege, where services or users are granted more access rights than necessary for their intended function, thereby creating a significant attack surface within the embedded system environment.
The technical mechanism exploited by an attacker involves leveraging specific command-line arguments provided to tcpdump, particularly the -z option. In many standard Linux distributions and embedded systems, this flag is used to specify a post-processing program that runs after packet capture completes. When combined with the elevated privileges granted due to the insecure permissions, an authenticated low-privileged user can inject arbitrary shell commands into this execution context. This results in remote code execution or local privilege escalation depending on the attack vector available to the adversary. The ability to execute commands as root without a password means that once authentication is achieved through any valid service account, the attacker gains full control over the underlying operating system of the gateway device.
From an operational impact perspective, this vulnerability compromises the integrity and confidentiality of the entire network infrastructure protected by the MBS-Solutions X-Series Gateway. An attacker with access to low-privileged services can pivot into a root shell, allowing them to install persistent backdoors, exfiltrate sensitive data traversing the gateway, modify firewall rules to allow unauthorized traffic, or disrupt critical network operations. In industrial control systems or enterprise networks where such gateways are deployed, this could lead to significant downtime, financial loss, and potential safety risks if physical processes are affected by compromised network controls. The lack of password protection for root execution further amplifies the risk, as it removes a common barrier that might otherwise delay or prevent exploitation attempts.
This vulnerability aligns with CWE-250, which describes Execution with Unnecessary Privileges, indicating that the software performs an action at a higher privilege level than required. It also relates to CWE-732, concerning Incorrect Permission Assignment for Critical Resource, as the file permissions on /usr/bin/tcpdump are configured too permissively for a low-privileged user context. In terms of adversary tactics, this exploitation path corresponds to MITRE ATT&CK technique T1068 Exploitation for Privilege Escalation and potentially T1548 Abuse Elevation Control Mechanism if the system relies on sudo or similar wrappers that are misconfigured. The use of tcpdump as a vector also touches upon T1072 Software Deployment Tools, where legitimate administrative utilities are abused to execute malicious payloads within trusted environments.
Mitigation strategies must focus immediately on correcting the file permissions for /usr/bin/tcpdump to ensure it is not executable by low-privileged service users without proper authentication. Administrators should audit all setuid binaries and sudo configurations to verify that they adhere to strict access control policies. Updating the firmware to a patched version released by MBS-Solutions, if available, is the primary remediation step as these updates typically address such permission misconfigurations. Additionally, implementing network segmentation can limit the exposure of low-privileged service interfaces to untrusted networks, reducing the likelihood that an attacker can reach the vulnerable component in the first place. Regular security audits and automated vulnerability scanning should be employed to detect similar privilege escalation vectors across all connected devices before they can be exploited.