OSGeo GeoServer: xml external entity flaw under attack

What is affected

OSGeo GeoServer is mostly run by companies, schools and public bodies, not on home computers. You are unlikely to have it yourself, but organisations that hold your data may. Breaches that start with flaws like this one are how personal data ends up leaked.

OSGeo GeoServer contains an improper restriction of XML external entity reference vulnerability that occurs when the application accepts XML input through a specific endpoint /geoserver/wms operation GetMap and could allow an attacker to define external entities within the XML request.

What an attacker can do

This is a xml external entity flaw. It lets an attacker make the system read local files or contact internal services while it processes a crafted XML document.

How it is reached

Over the internet or network

Access the attacker needs

No account needed

Does the victim have to do something?

No, works without the victim doing anything

What to do

1. At home: nothing to install. Keep your own devices updated and use a different password for every service, so that a breach at one organisation does not open your other accounts.
2. If you administer OSGeo GeoServer at work: apply the vendor's fix or mitigation now and review logs for signs of compromise, because the flaw was being exploited before it was listed.
3. If the product is past its support date and no fix exists, take it off the internet or retire it.

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

Vendor advisories and fixes

• github.comgithub.com/geoserver/geoserver/security/advisories/GHSA-fjf5-xgmq-5525
• osgeo-org.atlassian.netosgeo-org.atlassian.net/browse/GEOS-11922

How urgent is it

CISA added this vulnerability to its Known Exploited Vulnerabilities catalogue on December 11, 2025, which means there is reliable evidence of attacks in the wild. US federal agencies must fix it by January 1, 2026, a deadline that has already passed. That deadline does not bind anyone else, but it shows how seriously the agency rates it.

The EPSS model estimates a 61% probability that this flaw will be exploited somewhere in the next 30 days. That is higher than 99.1% of all scored vulnerabilities.

Its CVSS severity score is 9.8 out of 10 (critical), as recorded in the US National Vulnerability Database.

Technical description

GeoServer is an open source server that allows users to share and edit geospatial data. From version 2.26.0 to before 2.26.2 and before 2.25.6, an XML External Entity (XXE) vulnerability was identified. The application accepts XML input through a specific endpoint /geoserver/wms operation GetMap. However, this input is not sufficiently sanitized or restricted, allowing an attacker to define external entities within the XML request. This issue has been patched in GeoServer 2.25.6, GeoServer 2.26.3, and GeoServer 2.27.0.