Executive Summary

CVE-2026-30478 is a local privilege escalation vulnerability in GatewayGeo MapServer for Windows version 5 and earlier. It arises because the configuration file ms4w.conf, located in C:\ms4w, is writable by all users while the MapServer service runs with SYSTEM-level privileges.

An attacker with local non-privileged access can modify this configuration file to reference a malicious map file and a malicious Dynamic-Link Library (DLL) hosted on a remote machine. When the MapServer service loads the malicious DLL, it executes code with SYSTEM privileges, allowing the attacker to escalate their privileges to full system control.

• The attacker creates a crafted map file defining a plugin layer referencing a malicious DLL.
• The attacker creates a malicious DLL that executes arbitrary commands upon loading.
• The attacker modifies ms4w.conf to point to the malicious map file and DLL.
• The attacker triggers execution by invoking the map file locally, causing the malicious DLL to run with SYSTEM privileges.

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Impact Analysis

This vulnerability allows an attacker with local access to escalate their privileges from a non-privileged user to SYSTEM-level privileges on the affected Windows system running MapServer for Windows version 5 or earlier.

With SYSTEM privileges, the attacker gains full control over the system, enabling them to execute arbitrary code, install malware, access sensitive data, modify system configurations, and potentially compromise the entire environment.

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Detection Guidance

This vulnerability can be detected by checking for insecure permissions on the configuration file ms4w.conf located in the default installation directory C:\ms4w. Specifically, verify if ms4w.conf is writable by non-privileged users.

Additionally, detection involves checking if the configuration file contains suspicious entries pointing to remote map files or DLL plugins hosted on external shares.

You can also monitor for local curl requests to the MapServer CGI endpoint that reference unusual map files, such as:

• curl "http://127.0.0.1/cgi-bin/mapserv.exe?map=CVE-2026-30478"

Suggested commands to detect the vulnerability include:

• On Windows, check file permissions of ms4w.conf: icacls C:\ms4w\ms4w.conf
• Search ms4w.conf for suspicious remote map or DLL references: findstr /i "//" C:\ms4w\ms4w.conf
• Monitor local HTTP requests to the MapServer CGI endpoint for unusual map parameters using network monitoring tools or logs.

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Mitigation Strategies

Immediate mitigation steps include restricting the permissions on the ms4w.conf configuration file to prevent non-privileged users from modifying it.

Ensure that only trusted administrators have write access to C:\ms4w\ms4w.conf.

Remove any unauthorized or suspicious entries in ms4w.conf that reference remote map files or DLL plugins.

Avoid running the MS4W service with excessive privileges if possible, or apply additional security controls to limit the impact of a potential DLL injection.

Monitor for unusual activity such as unexpected DLL loads or local HTTP requests to the MapServer CGI endpoint.

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Compliance Impact

The provided information does not specify how this vulnerability impacts compliance with common standards and regulations such as GDPR or HIPAA.

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