CVE-2021-22915

Name: CVE-2021-22915
Creator: NVD / NIST
Published: 2021-06-11T16:15:11.913+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.8/10EPSS 1.74%

Last modified Jun 17, 2026

CVE-2021-22915 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. 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.. EPSS estimates a 1.74% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

9.8/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Probability

1.74%

74.8th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Nextcloud	Nextcloud Server	< 19.0.11
Nextcloud	Nextcloud Server	>= 20.0.0, < 20.0.10
Nextcloud	Nextcloud Server	>= 21.0.0, < 21.0.2
Fedoraproject	Fedora	33
Fedoraproject	Fedora	34

References

Timeline

Published: Jun 11, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-22915?

How severe is CVE-2021-22915?

CVE-2021-22915 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 1.74% probability of exploitation in the next 30 days.

How do I fix CVE-2021-22915?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-22915?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST