HOMEVULNERABILITIESCVE-2021-22915
CRITICAL

CVE-2021-22915

CWE-307Published: June 11, 2021· Updated: Jun 17, 2026

9.8
CVSS v3.1

Official 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.

NVD Source

Technical Analysis

CVE-2021-22915 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

A successful exploit results in complete confidentiality breach (data exposure), full integrity compromise (data manipulation), availability disruption (denial of service), with a CVSS base score of 9.8.

CVSS v3.1 Vector Breakdown

Exploitability
Attack VectorNetwork
Attack ComplexityLow
Privileges Req.None
User InteractionNone
ScopeUnchanged
Impact
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected Vendors & Products

Fedora1 product(s)
fedora
nextcloud1 product(s)
nextcloud server
Source: NVD CPE · 3 total CPE entries

Exploit & PoC Resources

NO KNOWN EXPLOITNo public exploit confirmed at this time
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
External links open in a new tab. Always verify in a controlled environment before use.

Official Patches & Advisories

ADVISORYhttps://hackerone.com/reports/1154003
ADVISORYhttps://hackerone.com/reports/1154003

All References (8)

→
https://hackerone.com/reports/1154003Permissions Required · Third Party Advisory
→
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/AGXGR6HYGQ6MZXISMJEHCOXRGRFRUFMA/
→
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/L6BO6P6MP2MOWA6PZRXX32PLWPXN5O4S/
→
https://nextcloud.com/security/advisory/?id=NC-SA-2021-009Broken Link
→
https://hackerone.com/reports/1154003Permissions Required · Third Party Advisory
→
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/AGXGR6HYGQ6MZXISMJEHCOXRGRFRUFMA/
→
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/L6BO6P6MP2MOWA6PZRXX32PLWPXN5O4S/
→
https://nextcloud.com/security/advisory/?id=NC-SA-2021-009Broken Link

Quick Facts

CVE IDCVE-2021-22915
CVSS Score9.8 / 10
SeverityCRITICAL
WeaknessCWE-307
CISA KEVNo
Affected2 vendor(s)
PublishedJun 11, 2021

Related CVEs (CWE-307)

CVE-2025-27456
9.8
CVE-2022-22810
9.8
CVE-2025-43863
9.8
CVE-2025-27449
9.8
CVE-2025-49195
9.8
CVE-2026-24445
9.8

Recommended Actions

  • →Apply vendor patches immediately
  • →Monitor CVE-2021-22915 in threat intel feeds
  • →Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWATCH.COM. CVE data is provided under the NVD usage policy.
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