CVE-2023-28999 : Exploit Details and Defense Strategies

This CVE record involves a vulnerability in Nextcloud that allows a malicious server to access E2EE folders due to a lack of authenticity of metadata keys.

Understanding CVE-2023-28999

This vulnerability in Nextcloud Desktop client, Nextcloud Android app, and Nextcloud iOS app versions allows a malicious server administrator to decrypt files, recover the folder structure, and add new files in an end-to-end encrypted folder.

What is CVE-2023-28999?

The CVE-2023-28999 vulnerability in Nextcloud arises from a lack of authenticity of metadata keys. This allows a malicious server admin to exploit the issue and gain unauthorized access to E2EE folders.

The Impact of CVE-2023-28999

The impact of CVE-2023-28999 is significant as it enables a malicious actor to decrypt files, recover folder structures, and insert new files into E2EE folders, compromising the confidentiality and integrity of data within the affected Nextcloud applications.

Technical Details of CVE-2023-28999

This vulnerability is categorized under CWE-325 (Missing Cryptographic Step) and has a CVSS v3.1 base score of 6.9, with high confidentiality and integrity impacts.

Vulnerability Description

The lack of authenticity of metadata keys in Nextcloud versions mentioned allows an attacker to exploit the vulnerability and gain access to E2EE folders, leading to unauthorized decryption and modification of files.

Affected Systems and Versions

Nextcloud versions affected by CVE-2023-28999 include Nextcloud Desktop client (3.0.0 to 3.8.0), Nextcloud Android app (3.13.0 to 3.25.0), and Nextcloud iOS app (3.0.5 to 4.8.0).

Exploitation Mechanism

The vulnerability is exploited by the malicious server administrator, who takes advantage of the lack of cryptographic steps in handling metadata keys to gain unauthorized access to E2EE folders within the Nextcloud applications.

Mitigation and Prevention

To mitigate the risks associated with CVE-2023-28999, immediate actions and long-term security practices should be implemented. Patching and updating the affected Nextcloud applications to the fixed versions is crucial.

Immediate Steps to Take

Users should update their Nextcloud Desktop client to version 3.8.0, Nextcloud Android app to version 3.25.0, and Nextcloud iOS app to version 4.8.0 to address the vulnerability and prevent unauthorized access to E2EE folders.

Long-Term Security Practices

Implementing robust cryptographic measures, enhancing authentication mechanisms, and regularly updating software can help prevent similar vulnerabilities in the future and enhance overall security posture.

Patching and Updates

Nextcloud has released fixes for this vulnerability in Nextcloud Desktop 3.8.0, Nextcloud Android 3.25.0, and Nextcloud iOS 4.8.0. Users are advised to apply these patches promptly to safeguard their systems from potential exploitation.