CVE-2020-8139 : Exploit Details and Defense Strategies

A missing access control check in Nextcloud Server < 18.0.1, < 17.0.4, and < 16.0.9 causes hide-download shares to be downloadable when appending /download to the URL.

Understanding CVE-2020-8139

This CVE identifies a vulnerability in Nextcloud Server versions prior to 18.0.1, 17.0.4, and 16.0.9 that allows unauthorized access to hide-download shares.

What is CVE-2020-8139?

The vulnerability in Nextcloud Server versions < 18.0.1, < 17.0.4, and < 16.0.9 enables the downloading of hide-download shares by simply adding /download to the URL.

The Impact of CVE-2020-8139

The vulnerability could lead to unauthorized access to sensitive information shared via hide-download links, compromising data confidentiality.

Technical Details of CVE-2020-8139

This section provides detailed technical insights into the CVE.

Vulnerability Description

A missing access control check in affected Nextcloud Server versions allows unauthorized download of hide-download shares by manipulating the URL.

Affected Systems and Versions

Product: Nextcloud Server
Versions Affected: < 18.0.1, < 17.0.4, and < 16.0.9

Exploitation Mechanism

The vulnerability can be exploited by appending /download to the URL of hide-download shares, bypassing access controls.

Mitigation and Prevention

Protect your systems and data from CVE-2020-8139 with the following measures.

Immediate Steps to Take

Upgrade Nextcloud Server to version 18.0.1, 17.0.4, or 16.0.9 to apply the necessary security patches.
Monitor and restrict access to hide-download shares to authorized users only.

Long-Term Security Practices

Regularly update and patch software to address security vulnerabilities promptly.
Implement access control mechanisms to prevent unauthorized access to sensitive data.

Patching and Updates

Stay informed about security advisories and updates from Nextcloud to ensure your systems are protected against known vulnerabilities.