CVE-2023-28833 : Security Advisory and Response

This CVE record was published on March 30, 2023, by GitHub_M, highlighting a vulnerability in Nextcloud server related to unrestricted filenames for logo or favicon as admin in the theming settings. The vulnerability is classified with a low base score of 2.4 and identified as CWE-22, involving the improper limitation of a pathname to a restricted directory (Path Traversal).

Understanding CVE-2023-28833

This section will delve into what CVE-2023-28833 is about and its significant impacts.

What is CVE-2023-28833?

Nextcloud server, an open-source home cloud implementation, faced a security issue where administrators could upload a logo or favicon with an unrestricted filename. This could potentially overwrite files in the appdata directory. Although administrators typically have file overwrite permissions, this vulnerability allowed exploitation by deceiving an admin into uploading a maliciously named file.

The Impact of CVE-2023-28833

The impact of this vulnerability is considered low, with no confidentiality or integrity impact. However, it poses a risk by providing a potential attack vector for malicious actors to manipulate and compromise the system.

Technical Details of CVE-2023-28833

Exploring the vulnerability in more detail, including the description, affected systems, and exploitation mechanism.

Vulnerability Description

The vulnerability in Nextcloud server allowed admins to upload files with unrestricted filenames, leading to the possibility of overwriting files in the appdata directory. This could be exploited by uploading maliciously named files to trick administrators.

Affected Systems and Versions

The affected versions of Nextcloud server include those below version 24.0.10 and versions between 25.0.0 and 25.0.4. Users utilizing these versions are susceptible to the risk posed by this vulnerability.

Exploitation Mechanism

By tricking an admin into uploading a file with a deceptive filename, attackers could exploit this vulnerability to overwrite critical files in the appdata directory, potentially gaining unauthorized access or causing system disruptions.

Mitigation and Prevention

Discover the steps and measures to mitigate the risks associated with CVE-2023-28833 and prevent potential exploits.

Immediate Steps to Take

It is recommended to upgrade Nextcloud Server to versions 24.0.10 or 25.0.4 to address the vulnerability. For users unable to upgrade immediately, refraining from ingesting logo files from untrusted sources can help reduce the risk of exploitation.

Long-Term Security Practices

Incorporating secure coding practices, regular security assessments, and awareness training for administrators can enhance the overall security posture and prevent similar vulnerabilities from occurring in the future.

Patching and Updates

Ensuring timely installation of security patches and updates provided by Nextcloud is crucial to addressing known vulnerabilities and strengthening the defense mechanisms within the server environment. Regularly monitoring security advisories and applying patches promptly can help mitigate risks effectively.