CVE-2023-39959 : Exploit Details and Defense Strategies

Nextcloud Server provides data storage for Nextcloud, an open source cloud platform. A vulnerability in Nextcloud Server versions prior to 25.0.9, 26.0.4, and 27.0.1 allows unauthenticated users to check the existence of calendars and address books through a DAV request. The issue has been patched in the mentioned versions.

Understanding CVE-2023-39959

This CVE identifies a security vulnerability in Nextcloud Server that permits unauthenticated users to determine the presence of calendars and address books on the platform.

What is CVE-2023-39959?

CVE-2023-39959 is a flaw in Nextcloud Server versions before 25.0.9, 26.0.4, and 27.0.1 that enables unauthorized users to disclose the existence of calendars or address books.

The Impact of CVE-2023-39959

The vulnerability could lead to privacy breaches, as attackers can gather information about the availability of specific data without proper authentication, potentially compromising user data confidentiality.

Technical Details of CVE-2023-39959

The details of the CVE include:

Vulnerability Description

The flaw allows unauthenticated users to send a DAV request, revealing whether specific calendars or address books exist on the Nextcloud Server.

Affected Systems and Versions

Nextcloud Server versions prior to 25.0.9, 26.0.4, and 27.0.1 are affected by this vulnerability.

Exploitation Mechanism

Unauthorized users can exploit this issue by triggering a DAV request to determine the presence of targeted calendars or address books.

Mitigation and Prevention

To address CVE-2023-39959, consider the following:

Immediate Steps to Take

Upgrade Nextcloud Server to versions 25.0.9, 26.0.4, or 27.0.1 to apply the necessary patch.
Regularly monitor security advisories for any updates related to Nextcloud Server.

Long-Term Security Practices

Implement proper access controls and authentication mechanisms to restrict unauthorized access.
Conduct regular security audits and penetration testing to identify and address vulnerabilities.

Patching and Updates

Ensure timely installation of security patches and updates provided by Nextcloud to prevent exploitation of known vulnerabilities.