CVE-2025-57878 is an unvalidated redirect vulnerability classified under CWE-601 affecting Esri Portal for ArcGIS versions 11.4 and below, including version 10.9.1. This vulnerability allows a remote, unauthenticated attacker to craft a malicious URL that appears to originate from a legitimate Esri Portal for ArcGIS instance but redirects the victim to an arbitrary external website. The core issue is that the application fails to properly validate or sanitize redirect URLs, enabling open redirect attacks. Such attacks can be leveraged to facilitate phishing campaigns by exploiting user trust in the legitimate domain, potentially leading users to malicious sites designed to steal credentials, deliver malware, or conduct other social engineering exploits. The CVSS v3.1 base score is 6.1 (medium severity), reflecting that the attack vector is network-based with low attack complexity and no privileges required, but user interaction is necessary (clicking the crafted link). The vulnerability impacts confidentiality and integrity by enabling credential theft or session hijacking through phishing, but does not directly affect availability. No known exploits are currently reported in the wild, and no patches have been linked yet. The scope is considered changed (S:C), indicating that the vulnerability affects components beyond the initially vulnerable component, potentially impacting user trust and security posture of the entire portal ecosystem.

For European organizations using Esri Portal for ArcGIS, this vulnerability poses a significant risk primarily through social engineering and phishing attacks. Since the portal is often used by government agencies, urban planners, environmental organizations, and private sector companies for geographic information system (GIS) data sharing and collaboration, a successful open redirect attack could lead to credential compromise or unauthorized access to sensitive spatial data. This could result in data breaches, loss of intellectual property, or manipulation of critical infrastructure information. The indirect impact includes erosion of user trust in the platform, potential regulatory penalties under GDPR if personal data is compromised, and operational disruptions if attackers leverage stolen credentials for further attacks. The fact that the vulnerability requires no authentication but does require user interaction means that phishing campaigns could be crafted to exploit this weakness at scale, especially targeting employees or partners who frequently access the portal.

To mitigate this vulnerability, European organizations should: 1) Immediately monitor for any suspicious URLs or phishing attempts that mimic their Esri Portal for ArcGIS domain. 2) Educate users about the risk of clicking on unexpected or suspicious links, emphasizing verification of URLs even if they appear to originate from trusted sources. 3) Implement web application firewall (WAF) rules to detect and block open redirect patterns or suspicious redirect parameters targeting the portal. 4) Restrict or validate redirect URLs on the server side by implementing a whitelist of allowed redirect destinations or by enforcing strict URL validation logic within the portal configuration or custom code. 5) Keep the Esri Portal for ArcGIS software up to date and apply any patches or updates released by Esri addressing this vulnerability as soon as they become available. 6) Employ multi-factor authentication (MFA) to reduce the impact of credential theft resulting from phishing. 7) Conduct regular phishing simulations and security awareness training tailored to the use of GIS platforms.