CVE-2025-49393 is a critical security vulnerability affecting Fetch Designs Sign-up Sheets software versions up to and including 2.3.2. The vulnerability arises from unsafe deserialization of untrusted data, which enables an attacker to perform object injection attacks remotely without requiring authentication or user interaction. Object injection vulnerabilities occur when an application deserializes data from untrusted sources without sufficient validation, allowing attackers to manipulate serialized objects to execute arbitrary code, escalate privileges, or disrupt application logic. In this case, the vulnerability affects the sign-up sheet functionality, which is likely used to manage event registrations or user sign-ups. The CVSS 3.1 base score of 9.8 reflects the vulnerability's critical nature, with network attack vector (AV:N), low attack complexity (AC:L), no privileges required (PR:N), no user interaction (UI:N), and full impact on confidentiality, integrity, and availability (C:H/I:H/A:H). Although no known exploits have been reported in the wild yet, the vulnerability's characteristics make it highly exploitable by attackers. The lack of available patches at the time of publication increases the urgency for organizations to implement interim mitigations. The vulnerability was reserved in June 2025 and published in November 2025, indicating recent discovery and disclosure. The absence of CWE identifiers suggests a need for further classification, but the nature of the issue clearly aligns with CWE-502 (Deserialization of Untrusted Data).

For European organizations, this vulnerability poses a significant risk, especially for those relying on Fetch Designs Sign-up Sheets for managing user registrations, event management, or internal workflows. Exploitation could lead to unauthorized remote code execution, data theft, manipulation of sign-up data, and potential disruption of services. Confidentiality breaches could expose sensitive personal or organizational data, while integrity violations could corrupt registration records or workflows. Availability impacts could result in denial of service, affecting business continuity. Sectors such as education, event management, healthcare, and government agencies using this software are particularly vulnerable. The critical severity and ease of exploitation mean attackers could rapidly compromise systems, potentially using them as footholds for broader network intrusions or ransomware deployment. The lack of known exploits currently provides a window for proactive defense but also means organizations must act swiftly before active exploitation emerges.

1. Monitor Fetch Designs official channels for security patches addressing CVE-2025-49393 and apply them immediately upon release. 2. Until patches are available, restrict network access to the Sign-up Sheets application by implementing firewall rules limiting inbound traffic to trusted IPs or VPNs. 3. Employ web application firewalls (WAFs) with custom rules to detect and block suspicious serialized object payloads or anomalous request patterns targeting the sign-up sheets. 4. Conduct thorough input validation and sanitization on all data received by the application, especially serialized objects, to prevent malicious deserialization. 5. Isolate the Sign-up Sheets application in a segmented network zone to limit lateral movement in case of compromise. 6. Regularly audit logs for unusual activity indicative of exploitation attempts, such as unexpected deserialization errors or abnormal user behavior. 7. Educate IT and security teams about the vulnerability specifics to enhance detection and response capabilities. 8. Consider temporary disabling or replacing the vulnerable sign-up functionality if feasible until a secure version is deployed.