MapServer up to 8.6.3 OpenLayers HTML Output src/maputil.c msBuildOnlineResource HTTP_X_FORWARDED_HOST HTML injection

Summaryinfo

A vulnerability classified as problematic was found in MapServer up to 8.6.3. This impacts the function msBuildOnlineResource of the file src/maputil.c of the component OpenLayers HTML Output. The manipulation of the argument HTTP_X_FORWARDED_HOST results in HTML injection. This vulnerability is cataloged as CVE-2026-54355. The attack may be launched remotely. There is no exploit available. Upgrading the affected component is advised.

Detailsinfo

A vulnerability, which was classified as problematic, was found in MapServer up to 8.6.3. Affected is the function msBuildOnlineResource of the file src/maputil.c of the component OpenLayers HTML Output. The manipulation of the argument HTTP_X_FORWARDED_HOST with an unknown input leads to a html injection vulnerability. CWE is classifying the issue as CWE-79. The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. This is going to have an impact on integrity. CVE summarizes:

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.

The advisory is shared for download at github.com. This vulnerability is traded as CVE-2026-54355 since 06/12/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. Successful exploitation requires user interaction by the victim. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1059.007.

Upgrading to version 8.6.4 eliminates this vulnerability.

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Productinfo

Name

• MapServer

Version

• 8.6.0
• 8.6.1
• 8.6.2
• 8.6.3

Website

• Product: https://github.com/MapServer/MapServer/

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