CVE-2022-31120 is a medium-severity vulnerability affecting Nextcloud Server, an open-source personal cloud solution widely used for file sharing and collaboration. The vulnerability stems from insufficient logging (CWE-778) in the audit log functionality, specifically related to federated share events. Federated sharing allows users on different Nextcloud instances to share files and folders seamlessly. In affected versions (prior to 22.2.7 and between 23.0.0 and before 23.0.4), these federated share events were not properly recorded in the audit logs. This incomplete logging creates a blind spot for administrators, as brute force attacks targeting federated shares could go undetected. Notably, this vulnerability exacerbates the impact of CVE-2022-31118, which likely involves a related security issue that can be exploited more effectively when logging is insufficient. The lack of comprehensive logging reduces the ability to detect, investigate, and respond to malicious activity, increasing the risk of prolonged unauthorized access or data compromise. There are no known workarounds, and remediation requires upgrading Nextcloud Server to versions 22.2.7, 23.0.4, or 24.0.0 or later, where the logging deficiencies have been addressed.

For European organizations, the insufficient logging vulnerability poses a significant risk to security monitoring and incident response capabilities. Nextcloud is popular in Europe, especially among public sector entities, educational institutions, and enterprises seeking GDPR-compliant cloud solutions. The inability to detect brute force attacks on federated shares means attackers could gain unauthorized access to sensitive data without triggering alerts, potentially leading to data breaches, intellectual property theft, or disruption of collaboration workflows. This risk is heightened in regulated sectors where audit trails are critical for compliance. Additionally, since this vulnerability compounds the effects of CVE-2022-31118, attackers may leverage chained exploits to escalate privileges or move laterally within networks. The lack of logging also impedes forensic investigations, making it difficult to assess the scope and impact of incidents. Overall, the vulnerability undermines the confidentiality and integrity of data stored and shared via Nextcloud, with potential reputational and financial consequences for affected organizations.

To mitigate this vulnerability, European organizations using Nextcloud should prioritize upgrading their Nextcloud Server installations to versions 22.2.7, 23.0.4, 24.0.0, or later as soon as possible. Since no workarounds exist, patching is the primary defense. Organizations should also review their current logging and monitoring configurations to ensure audit logs are enabled and properly collected, especially for federated sharing activities. Implementing external log aggregation and analysis tools can help detect anomalies that might not be captured internally. Additionally, organizations should conduct targeted security assessments focusing on federated share configurations and brute force detection mechanisms. Enhancing multi-factor authentication (MFA) for federated share users can reduce the risk of brute force success. Finally, organizations should update incident response playbooks to account for potential gaps in logging and emphasize proactive monitoring of federated share access patterns.