CVE-2022-41968 is a vulnerability classified under CWE-400 (Uncontrolled Resource Consumption) affecting Nextcloud Server, an open-source personal cloud server widely used for file sharing and collaboration. The flaw exists in versions prior to 23.0.10 and between 24.0.0 and 24.0.5, where the server fails to validate the length of calendar names before writing them to the database. This lack of validation allows an attacker to submit excessively large calendar name data, which the system then attempts to process and store. The consequence is a potential denial-of-service (DoS) condition caused by resource exhaustion, as the database and server resources are overwhelmed by the unnecessary data load. This can degrade system performance, cause crashes, or make the Nextcloud service unavailable to legitimate users. The vulnerability does not require authentication or user interaction, as it can be exploited by sending crafted requests directly to the server. Although no known exploits have been reported in the wild, the issue is patched in Nextcloud versions 23.0.10 and 24.0.5. No workarounds are currently available, making timely patching critical. The vulnerability primarily impacts the database layer and the server’s input validation mechanisms, highlighting a gap in input sanitization for calendar-related data fields.

For European organizations relying on Nextcloud for cloud storage, collaboration, and calendar management, this vulnerability poses a risk of service disruption. Resource exhaustion attacks can lead to denial of service, impacting business continuity, especially for organizations with high dependency on Nextcloud for daily operations. This could affect sectors such as government, education, healthcare, and enterprises that use Nextcloud for sensitive data management and scheduling. The unavailability of calendar services may disrupt scheduling and coordination, while broader server instability could affect file sharing and communication. Additionally, organizations with limited IT resources may face challenges in quickly identifying and mitigating the issue, increasing downtime risk. Although the vulnerability does not directly expose confidential data, the resulting service outages could indirectly affect operational integrity and availability, which are critical for compliance with European data protection regulations like GDPR. Furthermore, attackers could leverage this vulnerability as part of a multi-stage attack to distract or disable defenses while attempting other intrusions.

The primary mitigation is to upgrade Nextcloud Server to version 23.0.10 or 24.0.5 or later, where the vulnerability is patched. Organizations should prioritize patch management to ensure vulnerable versions are not in use. In addition, network-level protections such as rate limiting and input validation proxies can help mitigate the impact by restricting the size and frequency of calendar-related requests. Monitoring database performance and server resource utilization can provide early warning signs of exploitation attempts. Implementing Web Application Firewalls (WAFs) with custom rules to detect and block unusually large calendar name inputs can also reduce risk. Since no workarounds exist, organizations should also review their incident response plans to quickly address potential DoS conditions. Regular backups and failover mechanisms will help maintain availability if an attack occurs. Finally, educating administrators about this specific vulnerability and encouraging prompt updates will reduce exposure time.