What’s Vulnerable › Vulnerabilities
CVE-2026-54355: MapServer: Reflected XSS in OpenLayers HTML Output via `HTTP_X_FORWARDED_HOST`
- Severity: medium (CVSS 5.3 v4.0)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 0.5% probability of exploitation in the next 30 days
- Public exploit or detection template: none known
- Published: 2026-09-17 · updated 2026-09-30
- Weakness: CWE-79
Description
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.
Affected products
- MapServer: from 6.0, < 8.6.4
References
- https://github.com/MapServer/MapServer/commit/edc1033c7963fcffd160d85cf430f49aaf4a1374
- https://github.com/MapServer/MapServer/commit/ff17ef190caaeaa9002ac3d1c7969ec5315c345e
- https://github.com/MapServer/MapServer/pull/7517
- https://github.com/MapServer/MapServer/pull/7518
- https://github.com/MapServer/MapServer/releases/tag/rel-8-6-4
- https://github.com/MapServer/MapServer/security/advisories/GHSA-xqj6-vjqr-33vv
- https://mapserver.org/development/changelog/changelog-8-6.html#changelog-8-6
- https://github.com/MapServer/MapServer/security/advisories/GHSA-xqj6-vjqr-33vv
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