CVE-2023-30539 : Exploit Details and Defense Strategies

A security vulnerability has been identified in Nextcloud that allows users to set up workflows using restricted and invisible system tags. This can lead to improper access control, potentially impacting system security. Read on to understand the details of CVE-2023-30539 and how to mitigate the risks.

Understanding CVE-2023-30539

Nextcloud allows the setup of workflows using system tags that might have restricted access. This issue can be exploited to control access or grant unauthorized access.

What is CVE-2023-30539?

CVE-2023-30539 highlights an improper access control vulnerability in Nextcloud that could be used to manipulate file access control and retention rules based on system tags.

The Impact of CVE-2023-30539

The vulnerability could allow unauthorized users to bypass access restrictions and gain access to sensitive information, compromising the security and integrity of the system.

Technical Details of CVE-2023-30539

The vulnerability is categorized as CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:L with a base score of 6.5, indicating a medium severity level.

Vulnerability Description

Users can exploit the vulnerability to alter file access control and retention rules via system tags, potentially granting unauthorized access to restricted files.

Affected Systems and Versions

Nextcloud Server: < 24.0.11
Nextcloud Server: >= 25.0.0, < 25.0.5
Nextcloud Files automated tagging: >= 1.11.0, < 1.11.1
Nextcloud Files automated tagging: >= 1.12.0, < 1.12.1
Nextcloud Files automated tagging: >= 1.13.0, < 1.13.1
Nextcloud Files automated tagging: >= 1.14.0, < 1.14.2
Nextcloud Files automated tagging: >= 1.15.0, < 1.15.3
Nextcloud Files automated tagging: >= 1.16.0, < 1.16.1

Exploitation Mechanism

The vulnerability can be exploited by manipulating workflows using system tags to override access controls and retention rules.

Mitigation and Prevention

To address CVE-2023-30539, immediate actions and long-term security practices should be implemented.

Immediate Steps to Take

Upgrade Nextcloud Server to version 24.0.11 or 25.0.5
Upgrade Nextcloud Enterprise Server to versions specified
Upgrade Nextcloud Files automated tagging app to secure versions

Long-Term Security Practices

Users should regularly update their Nextcloud Server, apply patches, and maintain strong access control policies to prevent unauthorized access.

Patching and Updates

Users unable to upgrade should disable all workflow-related apps to mitigate the risk of exploitation.