Bug 2538316 (CVE-2026-54355)

Summary: CVE-2026-54355 MapServer: MapServer: Reflected Cross-Site Scripting via HTTP_X_FORWARDED_HOST
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: high    
Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in MapServer, a system for developing web-based GIS applications. This reflected Cross-Site Scripting (XSS) vulnerability occurs in the OpenLayers HTML output when the `HTTP_X_FORWARDED_HOST` value is not properly escaped. An unauthenticated attacker can craft a malicious URL that, when opened by a victim, executes arbitrary JavaScript in the context of the MapServer site. This could lead to unauthorized access to user sessions, tokens, and sensitive data.
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Description OSIDB Bzimport 2026-09-22 18:04:35 UTC 
MapServer is a system for developing web-based GIS applications. From 6.0 until 8.6.4, MapServer's OpenLayers HTML output for SERVICE=WMS&REQUEST=GetMap&FORMAT=application/openlayers reflects an attacker-controlled X-Forwarded-Host value received as HTTP_X_FORWARDED_HOST through msBuildOnlineResource(), processLine(), and the [mapserv_onlineresource] substitution in src/maputil.c and src/maptemplate.c without escaping it for a single-quoted JavaScript string. When the deployment trusts the forwarded header and does not configure a fixed ows_onlineresource or MS_ONLINERESOURCE value, embedded single quotes can escape the generated URL string. An unauthenticated attacker can craft a URL that executes arbitrary JavaScript in the MapServer site origin when opened by a victim, enabling access to sessions or tokens, same-origin data and requests, and actions as the victim. This issue is fixed in version 8.6.4.