CVE-2025-54353 is a Cross-site Scripting (XSS) vulnerability classified under CWE-79 that affects Fortinet FortiSandbox versions 4.0.x through 5.0.2. The vulnerability arises from improper neutralization of input during web page generation, allowing an attacker to inject malicious scripts via crafted HTTP requests. Since the vulnerability is exploitable remotely over the network without requiring authentication (AV:N/PR:N), but does require user interaction (UI:R), an attacker could trick a legitimate user into triggering the malicious payload. The impact includes limited confidentiality and integrity compromise, such as stealing session cookies, executing unauthorized commands within the context of the web application, or manipulating the FortiSandbox interface. The vulnerability does not affect availability. The CVSS v3.1 base score is 5.3 (medium), reflecting the moderate impact and ease of exploitation. No public exploits or patches are currently available, but the vulnerability is officially published and tracked. FortiSandbox is a security appliance used for advanced threat detection and sandboxing, often deployed in enterprise and critical infrastructure environments. Exploiting this vulnerability could allow attackers to bypass security controls or gain footholds within protected networks by leveraging the FortiSandbox management interface.

For European organizations, the vulnerability poses a moderate risk primarily to the confidentiality and integrity of FortiSandbox management sessions and data. Successful exploitation could enable attackers to execute unauthorized commands or scripts, potentially leading to unauthorized access or manipulation of sandboxed files and threat analysis results. This could undermine the effectiveness of threat detection and response capabilities, increasing the risk of undetected malware propagation or data leakage. Organizations in sectors such as finance, telecommunications, energy, and government that rely on FortiSandbox for advanced threat protection may face increased exposure. The lack of availability impact reduces immediate operational disruption risk, but the potential for stealthy compromise remains significant. The requirement for user interaction means phishing or social engineering could be used to trigger the attack, emphasizing the need for user awareness. The absence of known exploits in the wild currently lowers immediate threat but does not eliminate future risk, especially as exploit code could be developed following public disclosure.

1. Monitor Fortinet advisories closely and apply official patches or updates as soon as they become available to address CVE-2025-54353. 2. Implement strict input validation and output encoding on all web interfaces to prevent injection of malicious scripts. 3. Deploy Web Application Firewalls (WAFs) with rules specifically designed to detect and block XSS attack patterns targeting FortiSandbox management portals. 4. Restrict access to FortiSandbox web interfaces to trusted networks and VPNs, minimizing exposure to untrusted users. 5. Enforce multi-factor authentication (MFA) for all administrative access to FortiSandbox to reduce risk from compromised credentials. 6. Conduct user training to recognize phishing attempts and suspicious links that could trigger the vulnerability. 7. Regularly audit FortiSandbox logs and monitor for unusual activity indicative of exploitation attempts. 8. Consider network segmentation to isolate FortiSandbox appliances from general user networks to limit attack surface. 9. If possible, disable or limit unnecessary web interface features that process user input. 10. Prepare incident response plans that include scenarios involving FortiSandbox compromise.