What’s Vulnerable › Vulnerabilities

CVE-2021-32728: End-to-end encryption device setup did not verify public key

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.9% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2021-08-18 · updated 2026-06-17
• Weakness: CWE-295

Description

The Nextcloud Desktop Client is a tool to synchronize files from Nextcloud Server with a computer. Clients using the Nextcloud end-to-end encryption feature download the public and private key via an API endpoint. In versions prior to 3.3.0, the Nextcloud Desktop client fails to check if a private key belongs to previously downloaded public certificate. If the Nextcloud instance serves a malicious public key, the data would be encrypted for this key and thus could be accessible to a malicious actor. This issue is fixed in Nextcloud Desktop Client version 3.3.0. There are no known workarounds aside from upgrading.

Affected products

• Debian Linux: 10.0, 11.0
• Desktop Client: before 3.3.0 — fixed in 3.3.0

How to fix

Upgrade to a fixed version: Desktop Client 3.3.0. Check the vendor advisory for mitigations.

References

• https://github.com/nextcloud/desktop/pull/3338
• https://github.com/nextcloud/security-advisories/security/advisories/GHSA-f5fr-5gcv-6cc5
• https://hackerone.com/reports/1189162
• https://www.debian.org/security/2021/dsa-4974
• https://github.com/nextcloud/desktop/pull/3338
• https://github.com/nextcloud/security-advisories/security/advisories/GHSA-f5fr-5gcv-6cc5
• https://hackerone.com/reports/1189162
• https://www.debian.org/security/2021/dsa-4974

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