Home/CVE/The Nextcloud Desktop Client is a tool to synchronize files from Nextcloud Server with a computer. Clients using the Nex
CVE

CVE-2021-32728

The Nextcloud Desktop Client is a tool to synchronize files from Nextcloud Server with a computer. Clients using the Nex

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.

MEDIUM · CVSS 6.5 EPSS 0.00209
Schedule remediation
  • Public exploit or PoC is available
Sigma rules6 YARA rules0
⬡

Weakness Classification

CWE-295Improper Certificate Validation
▤

Affected Products & Versions

2
nextcloud desktop< 3.3.0
debian linuxall versions
⚠

Public Exploits & PoCs

2
pocgithub.com · GHSA-f5fr-5gcv-6cc5github.com
pochackerone.com · 1189162hackerone.com
◈

Sigma Hunt Rules

6
Exact rules name this CVE ID. Product rules name an affected product in their title. Related rules cover techniques used by actors who exploited this CVE. Showing the most relevant matches; the complete related set is on the full drill-down.
producthighUser Added to Remote Desktop Users Group
producthighNgrok Usage with Remote Desktop Service
productmediumInstallation of TeamViewer Desktop
productmediumDesktop.INI Created by Uncommon Process
productmediumPotential Remote Desktop Tunneling
productmediumNew Remote Desktop Connection Initiated Via Mstsc.EXE
▣

Scoring & Timeline

6.5
MEDIUM · CVSS v3.1 · security-advisories@github.com
View on NVD
Attack Vector
Network Adjacent Local Physical
Attack Complexity
Low High
Privileges Required
None Low High
User Interaction
None Required
Scope
Unchanged Changed
Confidentiality
None Low High
Integrity
None Low High
Availability
None Low High
Published to NVD18 Aug 2021 · 04:15 PM
CVSS VectorCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
🔗

References & Sources

2
Source URLs (vendor pages, mailing lists, write-ups). Exploit/PoC links are in their own section above to avoid duplication.
https://github.com/nextcloud/desktop/pull/3338PatchThird Party Advisory
https://www.debian.org/security/2021/dsa-4974Third Party Advisory
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