CVE-2025-40598 is a reflected Cross-Site Scripting (XSS) vulnerability identified in the SonicWall SMA 100 Series web interface, specifically affecting versions 10.2.1.15-81sv and earlier. This vulnerability arises from improper neutralization of user-supplied input during web page generation (CWE-79), allowing an unauthenticated remote attacker to inject and execute arbitrary JavaScript code within the context of the victim's browser session. The attack vector is network-based (AV:N), requires no privileges (PR:N), but does require user interaction (UI:R), such as clicking a crafted link or visiting a malicious web page. The vulnerability has a CVSS v3.1 base score of 6.1, indicating medium severity, with partial impact on confidentiality and integrity but no impact on availability. The scope is changed (S:C), meaning the vulnerability affects resources beyond the initially vulnerable component, potentially allowing the attacker to steal session cookies, perform actions on behalf of the user, or manipulate the web interface. No known exploits are currently reported in the wild, and no patches have been publicly linked yet. SonicWall SMA 100 Series devices are widely used as secure mobile access gateways, VPN concentrators, and remote access appliances, often deployed in enterprise and government environments to provide secure connectivity. The vulnerability's exploitation could lead to session hijacking, credential theft, or unauthorized actions within the management interface, posing significant risks to network security and user privacy.

For European organizations, the exploitation of CVE-2025-40598 could lead to unauthorized access to sensitive network management functions and user sessions, undermining the confidentiality and integrity of critical remote access infrastructure. Given the widespread use of SonicWall SMA 100 Series appliances in corporate and governmental networks across Europe, successful attacks could facilitate lateral movement within networks, data exfiltration, or disruption of secure remote access services. The vulnerability's requirement for user interaction means phishing or social engineering campaigns could be leveraged to target employees or administrators, increasing the risk of compromise. Additionally, the potential for session hijacking or manipulation of web interface actions could lead to unauthorized configuration changes or exposure of sensitive data. This risk is heightened in sectors with stringent data protection requirements under GDPR, where breaches could result in regulatory penalties and reputational damage.

European organizations should prioritize the following mitigation steps: 1) Immediately verify the SonicWall SMA 100 Series firmware version in use and plan for an upgrade to a patched version once available from SonicWall. 2) In the interim, restrict access to the SMA 100 Series web interface to trusted internal networks or VPNs, minimizing exposure to unauthenticated external attackers. 3) Implement strict web filtering and email security controls to reduce the risk of phishing attacks that could trigger user interaction with malicious payloads. 4) Employ Content Security Policy (CSP) headers and other browser-based protections to mitigate the impact of reflected XSS attacks. 5) Monitor logs for unusual access patterns or repeated attempts to exploit web interface parameters. 6) Educate users and administrators about the risks of clicking unsolicited links and the importance of verifying URLs before interaction. 7) Consider deploying Web Application Firewalls (WAFs) with custom rules to detect and block XSS attack vectors targeting the SMA interface. These measures, combined with timely patching, will reduce the attack surface and limit potential exploitation.