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

> An unauthenticated attacker can inject arbitrary HTML/JavaScript into users' browsers via crafted WMS URLs in MapServer's OpenLayers viewer.

- **Severity:** Medium 6.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 8 May 2026
- **Updated:** 8 May 2026
- **Also known as:** DEBIAN-CVE-2026-42030, GHSA-4g9f-ph64-hg2x, UBUNTU-CVE-2026-42030

## 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 (Improper Neutralization of Script-Related HTML Tags in a Web Page)

## Which versions are affected by CVE-2026-42030?

It affects 1 product.


Products: Osgeo Mapserver.

## How do I fix CVE-2026-42030?

Upgrade to a fixed version.

## 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](https://insights.sbomify.com/CVE-2010-2540/): Security feature bypass in n/a (critical 10.0)
- [CVE-2009-2281](https://insights.sbomify.com/CVE-2009-2281/): Memory corruption in n/a (critical 10.0)
- [CVE-2009-0839](https://insights.sbomify.com/CVE-2009-0839/): Memory corruption in n/a (critical 10.0)
- [CVE-2009-0840](https://insights.sbomify.com/CVE-2009-0840/): Memory corruption in n/a (critical 10.0)
- [CVE-2009-0841](https://insights.sbomify.com/CVE-2009-0841/): Path traversal in n/a (critical 10.0)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-42030 and fix it if it is affected.

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

Affected product: MapServer. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-42030/ (Markdown: https://insights.sbomify.com/CVE-2026-42030/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-42030
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-42030
- OSV: https://osv.dev/vulnerability/CVE-2026-42030

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-42030/
Summaries are generated and may contain mistakes; the official description above is the record.