CVE-2026-75164 Overview
CVE-2026-75164 is an arbitrary file read vulnerability in the /cgi-bin/ugwdownload.cgi endpoint of MBS-Solutions X-Serie Gateway firmware version V6_00_05. A remote authenticated user holding the low-privileged Standard role can retrieve arbitrary files from the device filesystem by supplying a crafted value in the file query string parameter. The flaw is classified under CWE-552: Files or Directories Accessible to External Parties.
Critical Impact
Any authenticated Standard-role user can read sensitive files from the gateway, including configuration data, credentials, and cryptographic material stored on the device.
Affected Products
- MBS-Solutions X-Serie Gateway firmware V6_00_05
- The vulnerable component is the ugwdownload.cgi CGI handler
- See the MBS X-Serie Product Page for hardware details
Discovery Timeline
- 2026-09-04 - CVE-2026-75164 published to the National Vulnerability Database
- 2026-09-08 - Last updated in NVD database
- Research repository: GitHub CVE-2026-75164 Research
Technical Details for CVE-2026-75164
Vulnerability Analysis
The ugwdownload.cgi handler serves file downloads based on the value supplied in the file HTTP query string parameter. The handler does not restrict the parameter to an allow-listed directory or filename set, and it does not enforce role-based access checks beyond basic authentication. As a result, a user in the low-privileged Standard role can request files well outside any intended download scope.
Because the endpoint runs with the privileges of the web server process on the embedded device, an attacker can retrieve system files such as /etc/passwd, service configuration files, VPN or authentication secrets, and any application data readable by that process. This exposure enables further attacks including credential reuse, lateral movement, and offline analysis of cryptographic material.
Root Cause
The root cause is missing authorization and insufficient input validation on the file parameter [CWE-552]. The CGI trusts caller-supplied paths and does not enforce that requesters possess a role appropriate for accessing sensitive device files.
Attack Vector
Exploitation requires network reachability to the gateway's web interface and valid credentials for any Standard-role account. The attacker issues an HTTP GET request to /cgi-bin/ugwdownload.cgi with the file parameter set to the target path on the device filesystem. No user interaction is required, and the request can be automated across many devices.
No public proof-of-concept exploit code has been published beyond the referenced research repository. See the GitHub CVE-2026-75164 Research for technical details.
Detection Methods for CVE-2026-75164
Indicators of Compromise
- HTTP GET requests to /cgi-bin/ugwdownload.cgi with a file parameter containing path traversal sequences such as ../ or absolute paths like /etc/.
- Repeated download requests from the same authenticated Standard-role session targeting non-standard file paths.
- Web server access logs showing successful HTTP 200 responses for ugwdownload.cgi requests referencing system configuration files.
Detection Strategies
- Parse gateway web server logs for ugwdownload.cgi requests where the file parameter references paths outside the expected download directory.
- Alert on any Standard-role account issuing requests to ugwdownload.cgi with parameter values matching sensitive filenames such as passwd, shadow, config, or .key.
- Correlate authentication events with subsequent CGI download requests to identify accounts abusing the endpoint shortly after login.
Monitoring Recommendations
- Forward gateway HTTP and authentication logs to a centralized SIEM or data lake for retention and correlation.
- Baseline normal download activity per user role and flag deviations, particularly Standard-role accounts accessing administrative files.
- Monitor for unusual outbound data volumes from gateway management interfaces that may indicate bulk file extraction.
How to Mitigate CVE-2026-75164
Immediate Actions Required
- Restrict network access to the gateway management interface to trusted administrative networks or VPN segments only.
- Audit all accounts holding the Standard role and disable any that are unused or shared.
- Rotate credentials, API keys, and cryptographic material that may have been readable through the ugwdownload.cgi endpoint.
- Review web server logs for prior exploitation attempts referencing the file parameter.
Patch Information
At the time of publication, no vendor advisory or fixed firmware release has been referenced in the CVE record. Contact MBS-Solutions through the MBS Solutions Overview page for firmware update availability and apply any released patch superseding V6_00_05 as soon as it becomes available.
Workarounds
- Block external access to /cgi-bin/ugwdownload.cgi at an upstream reverse proxy or firewall until a patch is deployed.
- Limit access to the management interface with IP allow-listing and place the gateway behind a VPN.
- Enforce least-privilege role assignment and remove the Standard role from any account that does not require file download functionality.
- Enable full request logging on the gateway and forward logs to a monitored collector for detection of exploitation attempts.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
