Summary
The WMS specification defines an sld=<url> parameter for GetMap, GetLegendGraphic and GetFeatureInfo operations for user supplied "dynamic styling". Enabling the use of dynamic styles, without also configuring URL checks, provides the opportunity for Service Side Request Forgery.
It is possible to use this for "Blind SSRF" on the WMS endpoint to steal NetNTLMv2 hashes via file requests to malicious servers.
Details
This vulnerability requires:
- WMS Settings dynamic styling being enabled
- Security URL checks to be disabled, or to be enabled and allowing
file:\\*access
Mitigation
The ability to reference an external URL location is defined by the WMS standard GetMap, GetFeatureInfo and GetLegendGraphic operations. These operations are defined by an Industry and International standard and cannot be redefined by the GeoServer application in isolation.
To disable dynamic styling on GeoServer 2.10.3 and GeoServer 2.11.1:
- Navigate to Services > WMS Settings page
- Locate Dynamic styling heading
- Select the Disable usage of SLD and SLD_BODY parameters in GET requests and user styles in POST checkbox.
Resolution
To allow dynamic styling safely on GeoServer 2.22.5 and GeoServer 2.23.2:
- Navigate to Security > URL Checks
- Enable URL Checks are enabled setting
- Check the user manual for examples of how to trust specific locations:
^https://styles\.server\.net/cartography/.*$ - Enable dynamic styling on the Services > WMS Settings page, deselect the Disable usage of SLD and SLD_BODY parameters in GET requests and user styles in POST checkbox.
Use of dynamic styling safely is on by default in GeoServer 2.24.0.
References
Impact
This vulnerability can be used to steal user NetNTLMv2 hashes which could be relayed or cracked externally to gain further access.
Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside. Typical impact: access to internal metadata services, internal APIs, or cloud credentials.
CVE-2023-41339 has a CVSS score of 5.3 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.22.5, 2.23.2); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Remediation advice
org.geoserver:gs-wms to 2.22.5 or later; org.geoserver:gs-wms to 2.23.2 or later; org.geoserver.web:gs-web-app to 2.22.5 or later; org.geoserver.web:gs-web-app to 2.23.2 or later
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is CVE-2023-41339? CVE-2023-41339 is a medium-severity server-side request forgery (SSRF) vulnerability in org.geoserver:gs-wms (maven), affecting versions < 2.22.5. It is fixed in 2.22.5, 2.23.2. Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside.
- How severe is CVE-2023-41339? CVE-2023-41339 has a CVSS score of 5.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which packages are affected by CVE-2023-41339?
org.geoserver:gs-wms(maven) (versions < 2.22.5)org.geoserver.web:gs-web-app(maven) (versions < 2.22.5)
- Is there a fix for CVE-2023-41339? Yes. CVE-2023-41339 is fixed in 2.22.5, 2.23.2. Upgrade to this version or later.
- Is CVE-2023-41339 exploitable, and should I be worried? Whether CVE-2023-41339 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2023-41339 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2023-41339?
- Upgrade
org.geoserver:gs-wmsto 2.22.5 or later - Upgrade
org.geoserver:gs-wmsto 2.23.2 or later - Upgrade
org.geoserver.web:gs-web-appto 2.22.5 or later - Upgrade
org.geoserver.web:gs-web-appto 2.23.2 or later
- Upgrade