6.5

CVE-2021-32728: debian debian_linux Improper Certificate Validation

CVSS: 6.5v3.1MediumModified
AliasesUBUNTU-CVE-2021-32728DEBIAN-CVE-2021-32728
Published 18-08-2021Last modified 03-08-2024
Open JSON

Vulnerability summary

CVE-2021-32728 is a medium (CVSS 6.5) Improper Certificate Validation vulnerability in debian debian_linux. EPSS estimates a 0.85% chance of exploitation in the next 30 days, higher than 57.5% of scored vulnerabilities. 2 public exploits are recorded.

Overall risk
36/100
0100
Medium · default modelHow is this calculated?
CVSS score
6.5/10
010
Medium · v3.1 (CVE.org)
EPSS score
0.85%
0%100%
Low · 0.00 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits2github, reference

Advisory lineage

Upstream 0 · Downstream 2
DSA-4974-1MGASA-2021-0421

Timeline

  1. 18-08-2021
    PublishedVulnerability first disclosed.
  2. 03-08-2024
    Last modifiedVulnerability information updated.

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.

CVSS metrics

5 scores · 4 sources · 2 versions

EPSS trend

Probability

0.85%

Chance of exploitation in the next 30 days

Percentile

58%

Versus all other CVEs

30-day change

0.00 pp

From 0.85% on 19-09-2026

19-09-202619-10-2026
EPSS score
0.85%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

2 found
  • githubUnverified

    Security Advisories

    Maturity: poc

  • referenceUnverified

    Exploit Reference (hackerone.com)

    Maturity: unknown

Weaknesses

CWE · root cause

Affected systems

Debian2 products
Nextcloud2 products
Ubuntu1 product
  • nextcloud-desktopAll versions (No fix recorded)

3 vendors · 5 products

References

7 links