CVE-2026-75165: MBS-Solutions X-Serie Gateway Disclosure

CVE-2026-75165 Overview

CVE-2026-75165 is a broken authorization vulnerability [CWE-285] in the /cgi-bin/wwwugw.cgi component of the MBS-Solutions X-Serie Gateway firmware V6_00_05. The flaw allows a remote authenticated user assigned the low-privileged Standard role to invoke hidden network diagnostic methods that are not exposed through the web interface. Specifically, attackers can call the ugw-ping and ugw-traceroute methods to conduct network reconnaissance and obtain sensitive information about internal network topology. The vulnerability requires network access and valid low-privileged credentials but no user interaction.

Critical Impact
Low-privileged authenticated users can invoke hidden CGI methods to perform network reconnaissance and disclose sensitive topology data from segments reachable by the gateway.

Affected Products

MBS-Solutions X-Serie Gateway firmware V6_00_05
/cgi-bin/wwwugw.cgi handler
Deployments exposing the web management interface to untrusted users

Discovery Timeline

2026-09-04 - CVE-2026-75165 published to NVD
2026-09-09 - Last updated in NVD database

Technical Details for CVE-2026-75165

Vulnerability Analysis

The MBS-Solutions X-Serie Gateway exposes a CGI endpoint at /cgi-bin/wwwugw.cgi that dispatches multiple internal methods based on request parameters. The web UI restricts network diagnostic tooling to administrative roles. However, the CGI handler does not enforce a matching authorization check server-side.

An authenticated user holding only the Standard role can craft direct HTTP requests that invoke the ugw-ping and ugw-traceroute methods. These methods return diagnostic output including reachable hosts, latency data, and intermediate hops. The output reveals internal network topology, live host addresses, and routing information that the Standard role is not intended to see.

The issue is categorized as improper authorization [CWE-285]. The vulnerability affects confidentiality but does not directly modify data or availability on the gateway itself.

Root Cause

The root cause is a client-side-only authorization model. The web application hides sensitive diagnostic actions from the Standard role at the UI layer but does not repeat the role check inside the wwwugw.cgi dispatcher. Any authenticated session token is accepted as sufficient authorization for every method the CGI supports.

Attack Vector

An attacker first obtains valid credentials for any Standard-role account on the gateway. The attacker then sends an HTTP request directly to /cgi-bin/wwwugw.cgi specifying the hidden method name (ugw-ping or ugw-traceroute) and a target address parameter. The gateway executes the diagnostic against the requested target and returns the results to the caller. Repeated invocations against internal address ranges enable mapping of reachable systems behind the gateway.

No exploitation code is published for CVE-2026-75165. Refer to the GitHub CVE-2026-75165 Research repository for the researcher's technical write-up.

Detection Methods for CVE-2026-75165

Indicators of Compromise

HTTP POST or GET requests to /cgi-bin/wwwugw.cgi containing the method parameters ugw-ping or ugw-traceroute from sessions authenticated as Standard-role users.
Bursts of diagnostic requests targeting sequential internal IP addresses, indicating network sweep activity.
Access to wwwugw.cgi from source addresses that do not normally administer the gateway.

Detection Strategies

Enable verbose HTTP access logging on the gateway management interface and alert on invocations of hidden CGI methods by non-administrative accounts.
Correlate authenticated session role with the CGI method invoked; flag any mismatch between UI-permitted actions and observed requests.
Monitor for outbound ICMP echo and UDP traceroute traffic originating from the gateway toward internal subnets that are not part of normal operations.

Monitoring Recommendations

Forward gateway web server logs to a centralized log platform for retention and query.
Baseline expected wwwugw.cgi method usage per user role and alert on deviations.
Track authentication events for Standard-role accounts and review any account that begins issuing diagnostic requests.

How to Mitigate CVE-2026-75165

Immediate Actions Required

Restrict management interface access to trusted administrative networks using firewall rules or VPN gating.
Audit all Standard-role accounts on the gateway and remove or disable unused accounts.
Rotate credentials for any Standard-role account suspected of misuse.
Contact MBS-Solutions for guidance on a fixed firmware release addressing CVE-2026-75165.

Patch Information

At the time of publication, no vendor advisory URL or patched firmware version is listed in the NVD entry for CVE-2026-75165. Consult the MBS X-Serie Product Page and vendor support channels for current firmware availability. Apply any successor to firmware V6_00_05 as soon as the vendor confirms the authorization fix.

Workarounds

Place the gateway management interface behind a reverse proxy or ACL that limits access to administrator source addresses only.
Remove the Standard role from users who do not require gateway self-service functions until a patch is applied.
Segment the gateway's downstream interfaces so that diagnostic probes cannot reach sensitive internal ranges.
Enable session-level monitoring to alert on non-administrative use of /cgi-bin/wwwugw.cgi.

bash

# Example: restrict access to the gateway management interface to a trusted admin subnet
iptables -A INPUT -p tcp --dport 443 -s 10.10.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP