CVE-2021-32728 : Security Advisory and Response

Nextcloud Desktop Client versions prior to 3.3.0 lack proper validation when setting up end-to-end encryption. An attacker could potentially gain access to encrypted data by serving a malicious public key.

Understanding CVE-2021-32728

This CVE details a vulnerability in Nextcloud Desktop Client that could lead to unauthorized access to encrypted data due to improper certificate validation.

What is CVE-2021-32728?

The issue occurs because the client fails to verify if a private key matches the previously downloaded public certificate, leading to data encryption for a malicious key.

The Impact of CVE-2021-32728

The vulnerability has a base severity rating of MEDIUM with HIGH confidentiality impact. If exploited, it could allow a malicious actor to access encrypted data.

Technical Details of CVE-2021-32728

The vulnerability is classified under CWE-295: Improper Certificate Validation.

Vulnerability Description

In versions before 3.3.0, the Nextcloud Desktop Client does not adequately verify private keys, potentially exposing encrypted data to unauthorized parties.

Affected Systems and Versions

Nextcloud Desktop Client versions prior to 3.3.0 are affected by this vulnerability.

Exploitation Mechanism

By serving a malicious public key, an attacker could intercept and decrypt data intended to be secure through end-to-end encryption.

Mitigation and Prevention

It is crucial to take immediate action to mitigate the risk posed by CVE-2021-32728.

Immediate Steps to Take

Upgrade to version 3.3.0 or above of the Nextcloud Desktop Client to address this vulnerability.

Long-Term Security Practices

Ensure that proper certificate validation is implemented in end-to-end encryption setups to prevent similar issues.

Patching and Updates

Regularly check for security advisories and updates from Nextcloud to stay protected against known vulnerabilities.