CVE-2023-48239 : Exploit Details and Defense Strategies

This article provides detailed information about CVE-2023-48239, a vulnerability in Nextcloud Server that allows users to make external storage mount points inaccessible for other users.

Understanding CVE-2023-48239

Nextcloud Server users could manipulate external storage settings, rendering them inaccessible for other users, impacting data availability.

What is CVE-2023-48239?

CVE-2023-48239 is a vulnerability in Nextcloud Server versions prior to 25.0.13, 26.0.8, 27.1.3, and corresponding Enterprise Server versions, allowing unauthorized manipulation of external storage configurations.

The Impact of CVE-2023-48239

This vulnerability poses a high risk as it enables a malicious user to update external storage settings, leading to data inaccessibility for other users and potential loss of important data.

Technical Details of CVE-2023-48239

The vulnerability is classified under CWE-284: Improper Access Control with a CVSS v3.1 base score of 8.5 (High).

Vulnerability Description

Starting from Nextcloud Server version 25.0.0, a user could modify external storage configurations, causing them to be inaccessible for all other users. The issue has been addressed in later versions.

Affected Systems and Versions

Nextcloud Server versions from 25.0.0 to 27.1.3 and corresponding Enterprise Server versions are affected by this vulnerability.

Exploitation Mechanism

A malicious user with low privileges can exploit this vulnerability remotely over a network without requiring user interaction, impacting data integrity and availability.

Mitigation and Prevention

To mitigate the risks associated with CVE-2023-48239, follow these preventive measures:

Immediate Steps to Take

Immediately upgrade Nextcloud Server and Enterprise Server to the patched versions to prevent unauthorized manipulation. Additionally, disabling the 'files_external' app can serve as a temporary workaround.

Long-Term Security Practices

Regularly update Nextcloud Server and Enterprise Server to the latest versions to ensure the critical security patches are applied promptly. Educate users on safe data storage practices to prevent data loss.

Patching and Updates

Stay informed about security advisories from Nextcloud and related platforms to deploy patches promptly and maintain a secure data storage environment.