XSS in Mapserver
CVE-2026-42030
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.
EPSS exploit prediction
EPSS: 0.003 (19.9th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 20th percentile — 19.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.003 · change: +0.000
Affected products
- Mapserver — versions >= 6.0, < 8.6.2
- Osgeo Mapserver
Weakness classification (CWE)
References
- github.com/MapServer/MapServer/security/advisories/GHSA-4g9f-ph64-hg2x (Exploit, Vendor Advisory)
- github.com/MapServer/MapServer/releases/tag/rel-8-6-2 (Product, Release Notes)
Frequently asked questions
- What is CVE-2026-42030?
- CVE-2026-42030 is a medium-severity vulnerability in Mapserver, classified under Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS). CVSS score: 6.1/10. Published 2026-05-08.
- How severe is CVE-2026-42030?
- Medium severity. CVSS v3 base score is 6.1 out of 10.