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Vulnerability · Published Sep 17, 2026 · Assigned by GitHub_M

CVE-2026-54355MapServer: Reflected XSS in OpenLayers HTML Output via `HTTP_X_FORWARDED_HOST`

Medium 5.3

In plain English

A medium-severity cross-site scripting in MapServer from MapServer. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 43% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)5.3Medium
Exploit odds (30 days)0.5%top 57.0% of all CVEs
Exploited in the wildNo reportsCISA SSVC: poc
Attack toolingNoneno public tooling known

Official 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 packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12mapserverno fix listedDEBIAN-CVE-2026-54355
Debian:13mapserverno fix listedDEBIAN-CVE-2026-54355
Debian:14mapserver8.6.4-1DEBIAN-CVE-2026-54355
Ubuntu:22.04:LTSmapserverno fix listedUBUNTU-CVE-2026-54355
Ubuntu:24.04:LTSmapserverno fix listedUBUNTU-CVE-2026-54355
Ubuntu:26.04:LTSmapserverno fix listedUBUNTU-CVE-2026-54355

Affected products (as reported)

VendorProductVersions
MapServer MapServer >= 6.0, < 8.6.4

Weakness: CWE-79 · Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N

References