CVE-2022-39364 is a medium-severity vulnerability affecting Nextcloud Server and Nextcloud Enterprise Server versions prior to 23.0.9 and 24.0.5, as well as versions prior to 22.2.10.5 for the Enterprise edition. Nextcloud is a widely used self-hosted productivity platform that provides file sharing and collaboration services. The vulnerability arises from the cleartext storage of sensitive information, specifically credentials used to connect to a SharePoint service, within the nextcloud.log file. This log file, if accessed by an attacker, can reveal these credentials, potentially allowing unauthorized access to integrated SharePoint resources. The root cause is related to CWE-312, which concerns the insecure storage of sensitive data in cleartext. The issue was addressed in the specified patched versions by removing or obfuscating sensitive credential information from logs. As a temporary mitigation, administrators can set the PHP configuration option `zend.exception_ignore_args = On` in the php.ini file to prevent sensitive arguments from being logged in exceptions. There are no known exploits in the wild targeting this vulnerability as of the published date. The vulnerability does not require user interaction or authentication to exploit if the attacker can read the log files, which implies that the attacker must have some level of access to the server or its file system to retrieve the logs. The scope of affected systems includes all Nextcloud Server and Enterprise Server deployments running the vulnerable versions that integrate with SharePoint services and generate logs containing credentials.

For European organizations, this vulnerability poses a risk primarily to confidentiality. If an attacker gains access to the nextcloud.log file, they can extract SharePoint service credentials, potentially leading to unauthorized access to sensitive documents and collaboration data stored on SharePoint. This could result in data breaches, intellectual property theft, or disruption of business operations. Given Nextcloud's popularity among enterprises and public sector organizations in Europe for secure file sharing and collaboration, the exposure of SharePoint credentials could facilitate lateral movement within networks or compromise integrated cloud services. The integrity and availability of Nextcloud services themselves are not directly impacted by this vulnerability, but the compromise of SharePoint credentials could indirectly affect these aspects if attackers manipulate or delete SharePoint data. The impact is heightened in environments where Nextcloud is used to bridge on-premises and cloud services, increasing the attack surface. Organizations with strict data protection regulations, such as GDPR, may face compliance and reputational risks if sensitive information is leaked due to this vulnerability.

Beyond applying the official patches in Nextcloud Server versions 23.0.9, 24.0.5, and Enterprise Server versions 22.2.10.5, 23.0.9, and 24.0.5, European organizations should implement the following specific measures: 1) Restrict access permissions to the nextcloud.log file strictly to trusted administrators and system processes to minimize the risk of unauthorized reading. 2) Regularly audit and monitor access logs and file integrity to detect any unauthorized access to log files. 3) Configure PHP with `zend.exception_ignore_args = On` as an immediate workaround to prevent sensitive data from being logged in exceptions until patches can be applied. 4) Review and rotate SharePoint service credentials that may have been exposed prior to patching to invalidate any compromised secrets. 5) Employ encryption at rest for log files and consider centralized, secure log management solutions that limit exposure of sensitive information. 6) Conduct security awareness training for administrators on the risks of logging sensitive data and best practices for credential management. 7) Evaluate the integration architecture between Nextcloud and SharePoint to ensure minimal credential exposure and consider using token-based authentication or vault solutions for credential storage. These targeted actions will reduce the risk of credential leakage and limit the attack surface associated with this vulnerability.