CVE-2023-39962 : Vulnerability Insights and Analysis

A vulnerability has been discovered in the Nextcloud Server that allows users to delete external storage mount points, potentially leading to denial of service attacks and unauthorized access to sensitive data.

Understanding CVE-2023-39962

This section provides insights into the nature of the vulnerability, its impact, technical details, and mitigation strategies.

What is CVE-2023-39962?

CVE-2023-39962 involves improper access control in Nextcloud Server, specifically versions prior to 19.0.13.10, 20.0.14.15, 21.0.9.13, 22.2.10.14, 23.0.12.9, 24.0.12.5, 25.0.9, 26.0.4, and 27.0.1. This vulnerability allows a malicious user to delete external storage mount points, affecting both personal and global storage configurations.

The Impact of CVE-2023-39962

The vulnerability has a CVSS base score of 7.7, indicating a high-severity issue. An attacker can exploit this flaw to render external storage inaccessible, impacting data availability. Moreover, unauthorized deletion of storage can lead to data loss and service disruption.

Technical Details of CVE-2023-39962

This section delves into the specifics of the vulnerability, including its description, affected systems and versions, as well as the exploitation mechanism.

Vulnerability Description

Nextcloud Server versions mentioned above are susceptible to improper access control, enabling users to delete external storage mount points. This action can result in the permanent loss of data stored in those locations.

Affected Systems and Versions

The affected versions of Nextcloud Server span from 19.0.0 to 27.0.1, with various releases falling within the vulnerable range. Users of these versions are urged to apply patches promptly to mitigate the risk.

Exploitation Mechanism

To exploit this vulnerability, a malicious actor with low privileges can target external storage configurations, deleting them without proper authorization. This activity can disrupt data accessibility and compromise the integrity of stored information.

Mitigation and Prevention

In light of CVE-2023-39962, adopting effective mitigation strategies is crucial to safeguard systems from potential threats.

Immediate Steps to Take

Users of the affected Nextcloud Server versions should apply the provided patches immediately to address the vulnerability. Additionally, disabling the 'app files_external' can serve as a temporary workaround to mitigate the risk of unauthorized storage deletion.

Long-Term Security Practices

Establishing robust access control mechanisms and regularly updating software can enhance the security posture of Nextcloud Server deployments, reducing the likelihood of similar vulnerabilities being exploited.

Patching and Updates

Nextcloud Server versions 25.0.9, 26.0.4, and 27.0.1, as well as Nextcloud Enterprise Server versions 19.0.13.10, 20.0.14.15, 21.0.9.13, 22.2.10.14, 23.0.12.9, 24.0.12.5, 25.0.9, 26.0.4, and 27.0.1 contain patches for CVE-2023-39962. Users are advised to update their installations promptly to secure their environments against potential exploitation.