CVE-2025-57876 is a stored Cross-site Scripting (XSS) vulnerability identified in Esri Portal for ArcGIS versions 11.4 and below, including version 10.9.1. This vulnerability arises from improper neutralization of input during web page generation (CWE-79), allowing a remote attacker with high privileges and authenticated access to inject malicious scripts embedded within files uploaded to the portal. When a victim loads such a malicious file, arbitrary JavaScript code can execute in their browser context. The attack requires both authentication and high privileges, limiting initial access but increasing the potential damage. Successful exploitation could disclose privileged tokens, enabling the attacker to escalate control and potentially gain full administrative access to the Portal for ArcGIS environment. The vulnerability has a CVSS 3.1 base score of 4.8 (medium severity), reflecting its moderate impact on confidentiality and integrity, no impact on availability, and the requirement for user interaction and high privileges. No public exploits are currently known, and no patches have been linked yet. Given the nature of the vulnerability, it primarily threatens the confidentiality and integrity of sensitive geospatial data and administrative controls within the Portal for ArcGIS platform, which is widely used for geographic information system (GIS) services and spatial data management.

For European organizations, especially those in government, urban planning, environmental monitoring, and critical infrastructure sectors that rely on Esri Portal for ArcGIS, this vulnerability poses a significant risk. Exploitation could lead to unauthorized disclosure of sensitive geospatial data, manipulation of spatial information, and potential disruption of GIS services critical for decision-making and operational continuity. The exposure of privileged tokens could allow attackers to assume administrative roles, leading to further compromise of internal networks and data integrity. Given the strategic importance of GIS data in sectors such as transportation, defense, and utilities across Europe, successful attacks could have cascading effects on national security, public safety, and economic activities. The requirement for high privileges and authentication reduces the likelihood of opportunistic attacks but raises concerns about insider threats or compromised privileged accounts. The medium severity rating suggests that while the vulnerability is serious, it is not trivially exploitable without prior access and user interaction.

European organizations should implement a multi-layered mitigation strategy: 1) Restrict and monitor administrative access to the Portal for ArcGIS, enforcing strict role-based access controls and multi-factor authentication to reduce the risk of credential compromise. 2) Conduct thorough input validation and sanitization on all uploaded files and user-generated content within the portal to prevent script injection. 3) Employ Content Security Policy (CSP) headers to limit the execution of unauthorized scripts in browsers accessing the portal. 4) Monitor logs and audit trails for unusual activities related to file uploads and administrative actions to detect potential exploitation attempts early. 5) Apply any vendor patches or updates promptly once available, and engage with Esri support to obtain interim mitigations or workarounds. 6) Educate privileged users about the risks of phishing and social engineering attacks that could lead to credential theft. 7) Consider network segmentation to isolate the Portal for ArcGIS environment from broader enterprise networks to contain potential breaches. These targeted measures go beyond generic advice by focusing on the specific attack vector and privilege requirements of this vulnerability.