CVE-2026-42030: MapServer is a system for developing web-based GIS applications

Routine

MEDIUM 6.1UPGRADE

CVE-2026-42030 is a medium-severity flaw (CVSS 6.1) affecting mapserver. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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

Why this priority

Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	6.1 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.2% (top 84%)
CISA exploited list	No
Weakness	CWE-80
Published	2026-05-08
Last modified	2026-06-17

Publisher (CNA): GitHub, Inc. · Vendor: osgeo

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-05-08 17:16 UTCPublished CVE record published
2026-06-17 10:47 UTCUpdated Record last modified

osgeo mapserver UPGRADE

Affected: >= 6.0.0 and < 8.6.2

Fixed in: 8.6.2

Safe to downgrade to: a release before 6.0.0

1. Check installed version

apt-cache policy mapserver || rpm -q mapserver || mapserver --version

2. UPGRADE to 8.6.2 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade mapserver

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade mapserver

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 6.0.0 (Debian / Ubuntu)

apt-cache madison mapserver sudo apt install mapserver=<VERSION_BEFORE_6.0.0> sudo apt-mark hold mapserver

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list mapserver sudo dnf downgrade mapserver-<VERSION_BEFORE_6.0.0> sudo dnf versionlock add mapserver

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-42030?

mapserver: upgrade to 8.6.2. Exact commands for each OS are on this page.

Is CVE-2026-42030 being exploited?

CVE-2026-42030 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-42030 affect?

CVE-2026-42030 affects mapserver. Severity is medium (CVSS 6.1). 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 t

How urgent is CVE-2026-42030?

Priority 30/100. Public exploit reference

Related CVEs

CVE-2026-45104 HIGH 7.5 UPGRADE MapServer is a system for developing web-based GIS applications

References

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