CVE-2023-41339 in gs-wms
Summary
by MITRE • 10/25/2023
GeoServer is an open source software server written in Java that allows users to share and edit geospatial data. The WMS specification defines an ``sld=`` 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. This vulnerability can be used to steal user NetNTLMv2 hashes which could be relayed or cracked externally to gain further access. This vulnerability has been patched in versions 2.22.5 and 2.23.2.
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Analysis
by VulDB Data Team • 11/15/2023
GeoServer serves as a critical component in geospatial data infrastructure, enabling organizations to publish and share spatial data through standardized web services. The vulnerability identified as CVE-2023-41339 specifically targets the Web Map Service implementation within GeoServer, where the SLD parameter functionality creates a potential attack vector for server-side request forgery. This flaw exists when dynamic styling capabilities are enabled without proper URL validation mechanisms, allowing malicious actors to manipulate the sld parameter to make unauthorized requests to internal systems. The vulnerability stems from insufficient input validation and sanitization of the SLD parameter, which is designed to accept user-supplied styling information for dynamic map rendering. When users provide SLD content through the sld parameter, the system processes these inputs without adequate restrictions on the URLs that can be referenced within the styling definitions. This oversight creates a pathway for attackers to craft malicious SLD documents that reference internal network resources or external malicious endpoints.
The operational impact of this vulnerability extends beyond simple data exposure, as it enables attackers to harvest NetNTLMv2 authentication hashes from internal systems. These hashes can be exploited through relay attacks or offline cracking attempts, potentially providing unauthorized access to network resources that would otherwise be protected by authentication mechanisms. The attack scenario involves crafting an SLD document that references a controlled external server, causing the GeoServer to make HTTP requests to that server and capture authentication credentials. This technique aligns with common attack patterns documented in the ATT&CK framework under credential access and lateral movement phases. The vulnerability particularly affects environments where GeoServer operates in network segments with access to internal authentication services or where the server can reach other internal systems that authenticate using NTLM. Security practitioners should note that the vulnerability affects both the GetMap, GetLegendGraphic, and GetFeatureInfo operations, providing multiple attack vectors for exploitation.
Organizations utilizing GeoServer must implement immediate remediation measures to address this vulnerability, with the most effective solution being the upgrade to patched versions 2.22.5 or 2.23.2. Beyond patching, administrators should enforce strict URL validation policies for SLD parameter inputs and consider implementing network segmentation to limit the potential impact of successful exploitation attempts. The vulnerability maps to CWE-918, which describes server-side request forgery vulnerabilities, and demonstrates how insufficient input validation can lead to authentication credential harvesting. Additional mitigations include configuring firewall rules to restrict access to internal resources from the GeoServer, implementing proper network access controls, and monitoring for unusual patterns in GeoServer logs that might indicate exploitation attempts. Security teams should also consider deploying intrusion detection systems capable of identifying malicious SLD content patterns and establish incident response procedures specifically addressing this class of vulnerability. The remediation process should include comprehensive testing of the patched versions to ensure that legitimate SLD functionality remains operational while preventing the exploitation vectors that were previously possible.