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CVE-2021-22915

CRITICAL
9.8
CVSS Score
Published: June 11, 2021 at 03:49 PM UTC
Updated: June 17, 2026 at 03:38 AM UTC
2 products affected across 2 vendorsFedoraNextcloud/server

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Severity
CRITICAL9.8
Exploit prediction
EPSS 2%

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Fedora· Fedora Projectrpm
95%
3334
Nextcloud/server· Nextcloudnextcloud-app
95%
v < 19.0.1120.0.0 ≤ v < 20.0.1021.0.0 ≤ v < 21.0.2
Vendor states this is fixed in 19.0.11 (unaffected)
Affected range stops below 20.0.10, so it looks safe — our inference, not a vendor statement
Affected range stops below 21.0.2, so it looks safe — our inference, not a vendor statement

References (4)

x_refsource_MISCPermissions RequiredThird Party Advisory
Source: [email protected]
https://hackerone.com/reports/1154003
Vendor Advisoryx_refsource_FEDORA
Source: [email protected]
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/AGXGR6HYGQ6MZXISMJEHCOXRGRFRUFMA/
Vendor Advisoryx_refsource_FEDORA
Source: [email protected]
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/L6BO6P6MP2MOWA6PZRXX32PLWPXN5O4S/
x_refsource_MISCBroken Link
Source: [email protected]
https://nextcloud.com/security/advisory/?id=NC-SA-2021-009

CVSS

9.8CRITICAL[email protected]
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
HIGH
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-307

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