No exploitation reportedFix available

CVE-2021-22915

Q: Is CVE-2021-22915 actively exploited?

Active exploitation of CVE-2021-22915 has not been confirmed. Its EPSS score was 1.7% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

Q: What is the CVSS score for CVE-2021-22915?

CVE-2021-22915 has a CVSS v3 base score of 9.8 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

No exploitation reported by the sources we read.

Published2021-06-11
Fixed in21.0.2 · 20.0.10 · 19.0.11
WeaknessCWE-307

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 before 19.0.11, 20.0.10, 21.0.2 is vulnerable to brute force attacks due to lack of inclusion of IPv6 subnets in rate-limiting considerations. This could potentially result in an attacker bypassing rate-limit controls such as the Nextcloud brute-force protection.

Timeline

dates in UTC

2021-06-1116:15CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 18:48 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-2021-22915?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-22915?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

Fedoraproject fedora

Branch	Affected	Fixed in	Source
33.x	= 33	no fix published	NVD
34.x	= 34	no fix published	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

NVDCVSS 3.19.8read 2026-10-23
NVDCVSS 2.05read 2026-10-23
CNAweakness (CWE)CWE-307read 2026-10-23
NVDweakness (CWE)CWE-307read 2026-10-23
FIRST EPSSEPSS score1.7 %2026-10-22

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Published: 2021-06-11
Last Modified: 2026-06-17
NVD status: Modified

Frequently asked questions

What is CVE-2021-22915?

Is CVE-2021-22915 actively exploited?

Active exploitation of CVE-2021-22915 has not been confirmed. Its EPSS score was 1.7% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-22915?

CVE-2021-22915 has a CVSS v3 base score of 9.8 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

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