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CVE-2021-22915

29
FAUCET Score

CVE-2021-22915 is a critical vulnerability affecting Nextcloud server versions prior to 19.0.11, 20.0.10, and 21.0.2, where rate-limiting mechanisms fail to properly account for IPv6 subnets. This oversight allows attackers to bypass brute-force protection, potentially leading to unauthorized access. With a CVSS score of 9.8 (CRITICAL), this vulnerability is easily exploitable over the network with low complexity, enabling full compromise of confidentiality, integrity, and availability. Despite its severity, there is currently no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion or media coverage.

Impacted Technologies

VendorProductVersion(s)CPE
< 19.0.11CPE matchmatch criteria
cpe:2.3:a:nextcloud:nextcloud_server:*:*:*:*:*:*:*:*
>= 20.0.0, < 20.0.10CPE matchmatch criteria
cpe:2.3:a:nextcloud:nextcloud_server:*:*:*:*:*:*:*:*
>= 21.0.0, < 21.0.2CPE matchmatch criteria
cpe:2.3:a:nextcloud:nextcloud_server:*:*:*:*:*:*:*:*
33CPE matchmatch criteria
cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*
34CPE matchmatch criteria
cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

9.8CRITICAL

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.74%
Probability of exploitation in next 30 days
EPSS Percentile
75.4%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0174 is in the 63rd percentile among its peer group of 36,897 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

hackerone.com / reports/1154003
Permissions RequiredThird Party Advisory
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/AGXGR6HYGQ6MZXISMJEHCOXRGRFRUFMA
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/L6BO6P6MP2MOWA6PZRXX32PLWPXN5O4S
nextcloud.com / security/advisory
Broken Link