PT-2021-6528 · Nextcloud+1 · Nextcloud Desktop Client+1

Rtod · Published 2021-08-18 · Updated 2023-08-30 · CVE-2021-32728

Positive Technologies (AI Summary)

CVSS v2.0

6.8

Medium

Base vector

AV:N/AC:L/Au:S/C:C/I:N/A:N

Name of the Vulnerable Software and Affected Versions Nextcloud Desktop Client versions prior to 3.3.0

Description The issue is related to the end-to-end encryption feature of the Nextcloud Desktop Client, where the client fails to check if a private key belongs to a previously downloaded public certificate. This allows a remote attacker to potentially access confidential data if the Nextcloud instance serves a malicious public key. The data would be encrypted for this key, making it accessible to a malicious actor.

Recommendations For versions prior to 3.3.0, upgrade to Nextcloud Desktop Client version 3.3.0 to fix the issue. As a temporary workaround, consider restricting access to the API endpoint used for downloading public and private keys until the upgrade is possible. Avoid using the end-to-end encryption feature with untrusted Nextcloud instances to minimize the risk of exploitation.

Exploit

Fix

Improper Certificate Validation

Weakness Enumeration

CWE-295

Related Identifiers

ALT-PU-2023-2019

ALT-PU-2023-4584

ALT-PU-2023-5197

BDU:2022-01788

CVE-2021-32728

DSA-4974-1

GHSA-F5FR-5GCV-6CC5

MGASA-2021-0421

Affected Products

Alt Linux

Nextcloud Desktop Client

References · 21

• 🔥 https://github.com/nextcloud/security-advisories/security/advisories/GHSA-f5fr-5gcv-6cc5 · Exploit
• 🔥 https://hackerone.com/reports/1189162 · Exploit
• https://github.com/nextcloud/desktop/pull/3338 · Patch
• https://osv.dev/vulnerability/CVE-2021-32728 · Vendor Advisory
• https://security-tracker.debian.org/tracker/CVE-2021-32728 · Vendor Advisory
• https://security-tracker.debian.org/tracker/source-package/nextcloud-desktop · Vendor Advisory
• https://cve.org/CVERecord?id=CVE-2021-32728 · Security Note
• https://debian.org/security/2021/dsa-4974 · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2021-32728 · Security Note
• https://ubuntu.com/security/CVE-2021-32728 · Vendor Advisory
• https://osv.dev/vulnerability/MGASA-2021-0421 · Vendor Advisory
• https://osv.dev/vulnerability/UBUNTU-CVE-2021-32728 · Vendor Advisory
• https://osv.dev/vulnerability/DEBIAN-CVE-2021-32728 · Vendor Advisory
• https://osv.dev/vulnerability/DSA-4974-1 · Vendor Advisory
• https://advisories.mageia.org/MGASA-2021-0421.html · Security Note