No exploitation reportedFix available

CVE-2021-32656

Q: Is CVE-2021-32656 actively exploited?

Active exploitation of CVE-2021-32656 has not been confirmed. Its EPSS score was 1.8% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

Q: What is the CVSS score for CVE-2021-32656?

CVE-2021-32656 has a CVSS v3 base score of 8.6 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N.

No exploitation reported by the sources we read.

Published2021-06-01
Fixed in21.0.2 · 20.0.10 · 19.0.11
WeaknessCWE-284

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

Nextcloud Server is a Nextcloud package that handles data storage. A vulnerability in federated share exists in versions prior to 19.0.11, 20.0.10, and 21.0.2. An attacker can gain access to basic information about users of a server by accessing a public link that a legitimate server user added as a federated share. This happens because Nextcloud supports sharing registered users with other Nextcloud servers, which can be done automatically when selecting the "Add server automatically once a federated share was created successfully" setting. The vulnerability is patched in versions 19.0.11, 20.0.10, and 21.0.2 As a workaround, disable "Add server automatically once a federated share was created successfully" in the Nextcloud settings.

Timeline

dates in UTC

2021-06-0122:15CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-32656?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-32656?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD

Nextcloud nextcloud server

Branch	Affected	Fixed in	Source
21.0	≥ 21.0.0, < 21.0.2	21.0.2	NVD
20.0	≥ 20.0.0, < 20.0.10	20.0.10	NVD
19.0	< 19.0.11	19.0.11	NVD

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

Update Nextcloud nextcloud server to 21.0.2 · 20.0.10 · 19.0.11

Detection

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: none listed

Sources

CNACVSS 3.18.6read 2026-10-23
NVDCVSS 3.18.6read 2026-10-23
NVDCVSS 2.05read 2026-10-23
CNAweakness (CWE)CWE-284read 2026-10-23
FIRST EPSSEPSS score1.8 %2026-10-23

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N
Published: 2021-06-01
Last Modified: 2026-06-17
NVD status: Modified

Frequently asked questions

What is CVE-2021-32656?

Is CVE-2021-32656 actively exploited?

Active exploitation of CVE-2021-32656 has not been confirmed. Its EPSS score was 1.8% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-32656?

CVE-2021-32656 has a CVSS v3 base score of 8.6 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N.

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