CVE-2021-37631 Explained : Impact and Mitigation

Deck, an open-source kanban style organization tool integrated with Nextcloud, experienced a vulnerability that allowed users to access circles without proper authorization. Upgrading to specified versions or disabling the plugin is recommended.

Understanding CVE-2021-37631

This vulnerability in Nextcloud Deck could potentially lead to unauthorized access to shared boards.

What is CVE-2021-37631?

In affected versions, the Deck application failed to check user membership in a Circle, permitting non-Circle members to access shared boards.

The Impact of CVE-2021-37631

The vulnerability poses a medium severity risk with a base score of 6.5, allowing unauthorized access to sensitive information.

Technical Details of CVE-2021-37631

The vulnerability is classified under CWE-639, Authorization Bypass Through User-Controlled Key.

Vulnerability Description

In Nextcloud Deck versions < 1.2.9, >= 1.3.0, < 1.4.4, and >= 1.5.0, < 1.5.1, non-Circle members could exploit the issue to gain unauthorized access to shared boards.

Affected Systems and Versions

Systems using Nextcloud Deck versions as specified are impacted by this vulnerability.

Exploitation Mechanism

The vulnerability is exploited by circumventing the membership check in Circles, allowing unauthorized access to shared boards.

Mitigation and Prevention

Users should take immediate action to safeguard their systems from this vulnerability.

Immediate Steps to Take

Upgrade Nextcloud Deck to versions 1.5.1, 1.4.4, or 1.2.9. If upgrading is not feasible, disabling the Deck plugin is advised.

Long-Term Security Practices

Implement robust access controls and regularly monitor for security updates and patches.

Patching and Updates

Stay informed about security advisories and apply patches promptly to mitigate potential risks.