CVE-2025-55103 is a stored Cross-site Scripting (XSS) vulnerability identified in Esri Portal for ArcGIS Enterprise Sites, specifically affecting versions 10.9.1 through 11.4. This vulnerability arises due to improper neutralization of input during web page generation (CWE-79), allowing a remote, authenticated attacker with high privileges to inject malicious files containing embedded JavaScript code. When such a file is loaded by a victim, the malicious script executes in the context of the victim’s browser. The attack requires user interaction (loading the malicious file) and privileges to upload or inject content, which limits exploitation to users with elevated access rights. Successful exploitation can lead to disclosure of privileged tokens, potentially granting the attacker full control over the Portal environment. The vulnerability has a CVSS 3.1 base score of 4.8 (medium severity), reflecting its moderate impact and exploitation complexity. No known exploits are currently reported in the wild, and no patches have been linked yet. The vulnerability affects a critical component used for managing and sharing geographic information system (GIS) data within organizations, making it a significant risk for entities relying on Esri’s Portal for ArcGIS Enterprise Sites for spatial data collaboration and operations.

For European organizations, this vulnerability poses a risk primarily to entities using Esri Portal for ArcGIS Enterprise Sites for GIS data management, including government agencies, urban planning departments, environmental monitoring bodies, and private sector companies involved in logistics, utilities, and infrastructure. Exploitation could lead to unauthorized access to sensitive spatial data and administrative control over the portal, potentially disrupting critical services or exposing confidential information. Given the high privileges required, the threat is more likely to originate from insider threats or compromised privileged accounts. The ability to execute arbitrary JavaScript could also facilitate further attacks such as session hijacking, privilege escalation, or lateral movement within the network. The medium CVSS score indicates a moderate risk, but the strategic importance of GIS data in sectors like transportation, energy, and public safety in Europe elevates the potential operational impact. Additionally, the cross-site scripting nature of the vulnerability could undermine user trust and compliance with data protection regulations such as GDPR if sensitive data is exposed or manipulated.

European organizations should implement several targeted mitigation strategies beyond generic advice: 1) Restrict and monitor high-privilege user accounts to minimize the risk of malicious file uploads; enforce strict access controls and use multi-factor authentication (MFA) for all privileged users. 2) Conduct thorough input validation and sanitization on all user-uploaded files and content within the Portal, employing web application firewalls (WAFs) with custom rules to detect and block suspicious payloads. 3) Implement Content Security Policy (CSP) headers to limit the execution of unauthorized scripts in users’ browsers. 4) Regularly audit and review portal activity logs to detect anomalous behavior indicative of exploitation attempts. 5) Coordinate with Esri for timely patch deployment once available and test updates in controlled environments before production rollout. 6) Educate privileged users about the risks of XSS and safe handling of portal content. 7) Segment the network hosting the Portal to limit lateral movement in case of compromise. These measures collectively reduce the attack surface and improve detection and response capabilities.