CVE-2025-48389 is a high-severity vulnerability affecting FreeScout, a free, self-hosted help desk and shared mailbox software. The vulnerability arises from improper handling of serialized data within the application prior to version 1.8.178. Specifically, FreeScout’s set function allows an attacker to pass a string containing a serialized object. When the get method is called to retrieve this option, the application deserializes the data without sufficient validation. This unsafe deserialization process can lead to arbitrary code execution on the affected system. The vulnerability is classified under CWE-502 (Deserialization of Untrusted Data), which is a common and dangerous security flaw that can allow attackers to execute malicious code remotely. The CVSS 4.0 base score is 8.6, indicating a high severity level, with an attack vector of network (AV:N), low attack complexity (AC:L), no privileges required (PR:H indicates high privileges required, but the vector suggests network attack), no user interaction, and high impact on confidentiality, integrity, and availability. The vulnerability was publicly disclosed on May 29, 2025, and has been patched in FreeScout version 1.8.178. No known exploits are currently reported in the wild, but the nature of the vulnerability makes it a critical risk for organizations running vulnerable versions of FreeScout. Attackers exploiting this flaw could execute arbitrary code remotely, potentially leading to full system compromise, data theft, or disruption of help desk services.

For European organizations, the impact of this vulnerability can be significant, especially for those relying on FreeScout for customer support and internal ticketing systems. Exploitation could lead to unauthorized access to sensitive customer data, internal communications, and potentially other connected systems within the corporate network. The arbitrary code execution capability means attackers could deploy malware, ransomware, or establish persistent backdoors, severely affecting business continuity and data integrity. Given that help desk systems often contain sensitive information about internal IT infrastructure and user credentials, a compromise could facilitate lateral movement within the network, escalating the severity of the breach. Additionally, disruption of help desk services can degrade customer trust and violate data protection regulations such as GDPR, leading to legal and financial consequences. The absence of known exploits in the wild currently provides a window for organizations to patch and mitigate the risk before active exploitation begins.

European organizations should immediately verify their FreeScout deployment versions and upgrade to version 1.8.178 or later to remediate this vulnerability. Beyond patching, organizations should implement strict input validation and sanitization controls to prevent untrusted serialized data from being processed. Employing application-layer firewalls or web application firewalls (WAFs) with rules to detect and block suspicious serialized payloads can provide an additional security layer. Restricting network access to FreeScout instances to trusted IP addresses and enforcing strong authentication and authorization policies will reduce the attack surface. Regularly auditing and monitoring logs for unusual deserialization activities or unexpected code execution attempts can help detect exploitation attempts early. Organizations should also consider isolating FreeScout instances within segmented network zones to limit potential lateral movement in case of compromise. Finally, maintaining an up-to-date inventory of software versions and applying security patches promptly is critical to minimizing exposure to such vulnerabilities.