CVE-2025-57877 is a reflected Cross-Site Scripting (XSS) vulnerability identified in Esri Portal for ArcGIS versions 11.4 and below, including version 10.9.1. This vulnerability arises due to improper neutralization of input during web page generation (CWE-79), allowing an attacker to inject malicious JavaScript code into the web application. Specifically, a remote attacker with authenticated administrative privileges can supply crafted input that is reflected in the web interface without adequate sanitization or encoding. When this malicious input is rendered in the victim's browser, it executes arbitrary JavaScript code within the security context of the Portal for ArcGIS web application. The vulnerability requires both authentication with high privileges and user interaction (the administrator must trigger the malicious input). The CVSS v3.1 base score is 4.8 (medium severity), reflecting the limited scope due to required privileges and user interaction, but also the potential for confidentiality and integrity impacts. The vulnerability does not affect availability. No known exploits are currently reported in the wild, and no patches have been linked yet. The vulnerability is significant because Portal for ArcGIS is a widely used geographic information system (GIS) platform that supports critical infrastructure, urban planning, and environmental monitoring. Exploitation could lead to session hijacking, unauthorized actions, or data leakage within the GIS portal environment.

For European organizations, this vulnerability poses a moderate risk primarily to those using Esri Portal for ArcGIS for managing sensitive geospatial data. The ability for an authenticated administrator to execute arbitrary JavaScript could lead to theft of session tokens, manipulation of GIS data, or unauthorized administrative actions. Given the critical role of GIS in sectors such as utilities, transportation, defense, and urban planning across Europe, exploitation could compromise the confidentiality and integrity of sensitive spatial data and operational workflows. While the attack requires administrative access, insider threats or compromised credentials could enable exploitation. The reflected XSS could also be leveraged as a stepping stone for further attacks within the network. However, the requirement for authentication and user interaction limits the attack surface, reducing the likelihood of widespread automated exploitation. Organizations handling critical infrastructure or government geospatial data should consider this vulnerability a significant concern due to the potential impact on data integrity and confidentiality.

To mitigate CVE-2025-57877, European organizations should: 1) Immediately review and restrict administrative access to Portal for ArcGIS, enforcing the principle of least privilege and strong authentication mechanisms such as multi-factor authentication (MFA). 2) Implement rigorous input validation and output encoding on all user-supplied data within the Portal for ArcGIS environment, especially for administrative interfaces. 3) Monitor and audit administrative activities and web application logs for unusual or suspicious input patterns that could indicate attempted exploitation. 4) Apply any available patches or updates from Esri promptly once released. 5) Employ Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts in the browser context. 6) Educate administrators on the risks of reflected XSS and the importance of cautious handling of URLs or input fields that may be manipulated. 7) Consider deploying Web Application Firewalls (WAFs) with rules tailored to detect and block reflected XSS payloads targeting Portal for ArcGIS. These measures, combined, will reduce the risk of exploitation and limit the potential damage from successful attacks.