CVE-2025-55105 is a stored Cross-site Scripting (XSS) vulnerability identified in Esri Portal for ArcGIS Enterprise Experience Sites, specifically affecting versions 10.9.1 through 11.4. 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 uploaded files. When a victim loads the compromised file or page, the embedded JavaScript executes in their browser context. This can lead to the disclosure of privileged tokens, which may allow the attacker to escalate privileges and gain full control over the Portal environment. The vulnerability requires high privileges to exploit and user interaction, as the victim must load the malicious content for the script to execute. The CVSS 3.1 base score is 4.8 (medium severity), reflecting network attack vector, low attack complexity, high privileges required, and user interaction needed. The scope is changed, indicating that the vulnerability affects components beyond the initially vulnerable module. No known exploits are currently reported in the wild, and no patches are linked yet, suggesting that organizations should prioritize monitoring and mitigation efforts. The vulnerability impacts the confidentiality and integrity of the Portal environment but does not directly affect availability. Given the critical role of Esri Portal for ArcGIS in geospatial data management and enterprise GIS deployments, exploitation could lead to significant unauthorized access and data compromise within affected organizations.

For European organizations, especially those in government, utilities, transportation, environmental monitoring, and critical infrastructure sectors that rely heavily on Esri's ArcGIS Enterprise solutions, this vulnerability poses a significant risk. Successful exploitation could lead to unauthorized disclosure of sensitive geospatial data, manipulation of GIS services, and potential disruption of decision-making processes dependent on accurate spatial information. The ability to gain full control over the Portal could allow attackers to alter or delete critical datasets, inject further malicious content, or pivot to other internal systems. Given the high privileges required, the threat is more pronounced in environments where multiple users have elevated access or where access controls are insufficiently enforced. The medium CVSS score suggests moderate urgency, but the potential for privilege escalation and full Portal compromise elevates the risk profile. Additionally, the cross-site scripting nature of the vulnerability could facilitate phishing or social engineering attacks targeting privileged users. European organizations must consider the regulatory implications, including GDPR, as unauthorized access or data leakage involving personal or sensitive data could lead to compliance violations and financial penalties.

To mitigate this vulnerability effectively, European organizations should: 1) Immediately review and restrict high-privilege user accounts to the minimum necessary, enforcing strict role-based access controls and multi-factor authentication to reduce the risk of credential compromise. 2) Implement rigorous input validation and sanitization on all file uploads and user-generated content within the Portal environment, even if patches are not yet available. 3) Monitor Portal logs and user activity for unusual behavior indicative of attempted exploitation, such as unexpected file uploads or script execution attempts. 4) Educate privileged users about the risks of loading untrusted files or content within the Portal and encourage cautious behavior. 5) Engage with Esri support and subscribe to security advisories to promptly apply patches or updates once released. 6) Consider deploying web application firewalls (WAFs) with custom rules to detect and block malicious script payloads targeting the Portal. 7) Conduct regular security assessments and penetration testing focused on the ArcGIS Enterprise environment to identify and remediate similar vulnerabilities proactively. 8) Isolate the Portal environment within segmented network zones to limit lateral movement if compromise occurs.