How severe is CVE-2025-21621?

CVE-2025-21621 has a CVSS score of 6.1/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2025-21621?

CVE-2025-21621 affects the following packages: org.geoserver.web:gs-web-app (Maven), org.geoserver:gs-wms (Maven). Ecosystems affected: Maven.

How do I fix CVE-2025-21621?

Update org.geoserver.web:gs-web-app to 2.25.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-21621 is resolved across your whole dependency graph.

How do I detect CVE-2025-21621 in my Maven dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.geoserver.web:gs-web-app, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2025-21621 if there is no patch (or I can't update yet)?

Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Is CVE-2025-21621 actively exploited in the wild?

No public exploit code has been indexed for CVE-2025-21621 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2025-21621?

CVE-2025-21621 has an EPSS (Exploit Prediction Scoring System) score of 0.3%, placing it in the 20th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2025-21621?

CVE-2025-21621 is classified as Cross-site Scripting (XSS) (CWE-79). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2025-21621 published, and has it been updated?

CVE-2025-21621 was published on November 25, 2025 and was last updated on August 12, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

☕

☕ Maven

Not in CISA KEV

MEDIUM severity

CVE-2025-21621 — gs-web-app

MEDIUMFix: geoserver/geoserver@dc9ff1c

CVE-2025-21621 is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in org.geoserver.web:gs-web-app. A fix is available for org.geoserver.web:gs-web-app — see the affected versions and patch details below.

GeoServer Reflected Cross-Site Scripting (XSS) vulnerability in WMS GetFeatureInfo HTML format

Also known asGHSA-w66h-j855-qr72

Published

Nov 25, 2025

Updated

Aug 12, 2026

Affected

2 pkgs

Patched

2 / 2

Exploits

None indexed

Exploitation data as of Sep 26, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2025-21621.

EPSS Exploitation Probability

via FIRST.org ↗

0.3%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs20th percentile — riskier than 20% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2025-21621 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 379,842 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

2 pkgs affected

☕org.geoserver.web:gs-web-app☕org.geoserver:gs-wms

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

Description

Summary

A reflected cross-site scripting (XSS) vulnerability exists in the WMS GetFeatureInfo HTML output format that enables a remote attacker to execute arbitrary JavaScript code in a victim's browser through specially crafted SLD_BODY parameters.

Details

The WMS service setting that controls HTML auto-escaping is either disabled by default, or completely missing, in the affected versions (see workarounds).

Impact

If an attacker can control a script that is executed in the victim's browser, then they can typically fully compromise that user. Amongst other things, the attacker can:

Perform any action within the application that the user can perform.
View any information that the user is able to view.
Modify any information that the user is able to modify.
Initiate interactions with other application users, including malicious attacks, that will appear to originate from the initial victim user.

Workarounds

Changing any of the following WMS service settings should mitigate this vulnerability in most environments:

Enable GetFeatureInfo HTML auto-escaping (available in GeoServer 2.21.3+ and 2.22.1+)
Disable dynamic styling
Disable GetFeatureInfo text/html MIME type

References

https://osgeo-org.atlassian.net/browse/GEOS-11297 https://github.com/geoserver/geoserver/pull/7406

Affected Packages

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`org.geoserver.web:gs-web-app`	all versions	2.25.0`org.geoserver.web:gs-web-app:2.25.0`
☕Maven	`org.geoserver:gs-wms`	all versions	2.25.0`org.geoserver:gs-wms:2.25.0`

Affected Products

1 product · 1 configurations

Application

geoservergeoserver

< 2.25.0

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.geoserver.web:gs-web-app, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update org.geoserver.web:gs-web-app to 2.25.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-21621 is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Frequently Asked Questions

### Summary A reflected cross-site scripting (XSS) vulnerability exists in the WMS GetFeatureInfo HTML output format that enables a remote attacker to execute arbitrary JavaScript code in a victim's browser through specially crafted SLD_BODY parameters. ### Details The WMS service setting that controls HTML auto-escaping is either disabled by default, or completely missing, in the affected versions (see workarounds). ### Impact If an attacker can control a script that is executed in the victim's browser, then they can typically fully compromise that user. Amongst other things, the attacke