CVE-2025-57879 is an unvalidated redirect vulnerability classified under CWE-601 affecting Esri Portal for ArcGIS versions 11.4 and below, specifically noted in version 10.9.1. This vulnerability allows a remote, unauthenticated attacker to craft malicious URLs that redirect users to arbitrary external websites without validation. The core issue lies in the portal's failure to properly validate redirect targets, enabling attackers to exploit this behavior to facilitate phishing attacks by tricking users into visiting malicious sites under the guise of a legitimate Esri Portal URL. The vulnerability has a CVSS 3.1 base score of 6.1, indicating a medium severity level. The vector metrics are AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N, meaning the attack can be launched remotely over the network without privileges, requires user interaction (clicking the malicious link), and impacts confidentiality and integrity with a scope change. There are no known exploits in the wild at the time of publication, and no official patches have been linked yet. The vulnerability primarily threatens the trustworthiness of the portal's URLs, potentially leading to credential theft or malware delivery through social engineering rather than direct system compromise or data breach.

For European organizations using Esri Portal for ArcGIS, this vulnerability poses a significant risk to user trust and security posture. Since the portal is often used by government agencies, urban planners, environmental organizations, and private sector companies for geographic information system (GIS) data management and sharing, a successful phishing campaign leveraging this vulnerability could lead to credential compromise, unauthorized access to sensitive geospatial data, or broader network infiltration. The medium severity reflects that while direct system compromise is unlikely, the indirect consequences of phishing—such as data leakage or lateral movement—can be severe. European entities involved in critical infrastructure, urban planning, or environmental monitoring are particularly at risk, as attackers could use the open redirect to impersonate trusted portals and harvest credentials or distribute malware. Additionally, the scope change in the CVSS vector indicates that exploitation could affect resources beyond the initially targeted system, amplifying potential impact.

European organizations should implement several targeted mitigations beyond generic advice: 1) Monitor and audit all URLs generated by the Portal for ArcGIS to detect and block suspicious redirect parameters. 2) Employ web application firewalls (WAFs) with custom rules to detect and block open redirect attempts by validating redirect destinations against an allowlist of trusted domains. 3) Educate users about the risk of clicking on unexpected or suspicious links, especially those purporting to come from the Esri Portal. 4) Implement multi-factor authentication (MFA) on the portal to reduce the impact of credential theft resulting from phishing. 5) Regularly review and update URL handling logic in custom integrations or extensions of the portal to ensure no additional redirect vulnerabilities exist. 6) Stay alert for official patches or advisories from Esri and apply them promptly once available. 7) Use email security solutions that can detect and quarantine phishing attempts leveraging this vulnerability. These steps collectively reduce the risk of exploitation and limit the potential damage from successful phishing campaigns.