CVE-2026-42030 MapServer: Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS) in OpenLayers viewer

What is CVE-2026-42030?

CVE-2026-42030 is a medium-severity cross-site scripting vulnerability in MapServer, published on 8 May 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

Official description

MapServer is a system for developing web-based GIS applications. From version 6.0 to before version 8.6.2, a reflected XSS vulnerability in MapServer's WMS server allows an unauthenticated attacker to inject arbitrary HTML/JavaScript into the browser of any user who opens a crafted WMS URL. The vulnerability is triggered via FORMAT=application/openlayers combined with an unsanitized SRS parameter in WMS 1.3.0 requests. This issue has been patched in version 8.6.2.

Weakness: CWE-80

Which versions are affected by CVE-2026-42030?

It affects 1 product.

Products include Osgeo Mapserver.

How do I fix CVE-2026-42030?

Upgrade to a fixed version.

Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.

Is CVE-2026-42030 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-42030 exists.

Other vulnerabilities in MapServer

• CVE-2010-2540 Security feature bypass in n/a Critical 10.0
• CVE-2009-2281 Memory corruption in n/a Critical 10.0
• CVE-2009-0839 Memory corruption in n/a Critical 10.0
• CVE-2009-0840 Memory corruption in n/a Critical 10.0
• CVE-2009-0841 Path traversal in n/a Critical 10.0

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as DEBIAN-CVE-2026-42030, GHSA-4g9f-ph64-hg2x, UBUNTU-CVE-2026-42030.