CVE-2023-25821 Explained : Impact and Mitigation

This CVE affects Nextcloud, an Open Source private cloud software, where certain versions have an issue with Improper Access Control allowing reshare permissions to change download permissions.

Understanding CVE-2023-25821

This vulnerability in Nextcloud's versions 24.0.4 and below, and 25.0.0 and below, can potentially lead to unauthorized access to shared files due to improper access control configuration.

What is CVE-2023-25821?

The vulnerability, categorized under CWE-284: Improper Access Control, allows users to bypass secure view settings for internal shares by altering reshare permissions. This could result in confidentiality risks as unauthorized users may gain access to sensitive data.

The Impact of CVE-2023-25821

With a CVSS score of 5.7 (MEDIUM), this vulnerability poses a moderate risk, especially on systems where confidentiality is crucial. If exploited, it could lead to unauthorized viewing of files shared within the Nextcloud platform.

Technical Details of CVE-2023-25821

The details of this CVE include the affected systems, how the vulnerability can be exploited, and the recommended mitigation strategies.

Vulnerability Description

The vulnerability allows resharing permissions to override secure view settings, potentially exposing sensitive data to unauthorized parties. This could lead to improper access to confidential files within the affected Nextcloud versions.

Affected Systems and Versions

Versions of Nextcloud affected by this vulnerability include 24.0.4 to 24.0.7 and 25.0.0 to 25.0.1. Users running these versions are advised to update to version 24.0.7 or 25.0.1 to patch the security flaw.

Exploitation Mechanism

The vulnerability can be exploited by a user with reshare permissions altering the download permissions, thereby bypassing secure view settings and gaining unauthorized access to shared files within the Nextcloud platform.

Mitigation and Prevention

To address CVE-2023-25821 and enhance overall security posture, immediate steps must be taken to mitigate the risks and prevent potential exploitation.

Immediate Steps to Take

Users of affected Nextcloud versions should update their software to versions 24.0.7 or 25.0.1, where the vulnerability has been patched. This update will prevent unauthorized access to shared files through reshare permission manipulation.

Long-Term Security Practices

In the long term, organizations using Nextcloud should implement robust access control measures, regularly update the software, and educate users about secure sharing practices to prevent similar vulnerabilities from being exploited in the future.

Patching and Updates

Regularly applying software updates and security patches provided by Nextcloud is crucial to ensure that known vulnerabilities are addressed promptly, reducing the risk of exploitation and maintaining a secure cloud environment.