CVE intelligence and bounded remediation
CVE-2021-22915 — Nextcloud Nextcloud Server security vulnerability
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.
- Severity
- Critical
- CVSS
- 9.8 (3.1)
- Published
- 2021-06-11
- CISA KEV
- Not currently listed
- Ecosystem
- software/application
- Weaknesses
- CWE-307
Affected products
- nextcloud / nextcloud_server
- fedoraproject / fedora / 33
- fedoraproject / fedora / 34
Showing 3 representative product identities from 5 source matches. Confirm exact affected versions with the linked vendor and NVD evidence.
Matched remediation archetype
Authentication bypass and missing authentication
This catalog composition supplies bounded fallback guidance. Explicitly reviewed curated workflows load with the complete record below.
Check exposure
- Map every affected endpoint and protocol path, including alternate ports, legacy routes, recovery flows, service accounts, and machine-to-machine access.
- Confirm which deployments enable the affected authentication mode and whether the interface is reachable from untrusted networks.
- Review session, token, credential, and proxy trust configuration without attempting account takeover.
Remediate safely
- Apply the supported fix and centralize fail-closed authentication before protected request handling.
- Remove default or embedded credentials, rotate affected secrets and sessions, and bind authentication decisions to the intended audience and channel.
- Add negative tests for alternate routes, malformed or absent credentials, recovery flows, and proxy-derived identity.
Authoritative sources
Complete CVE record and remediation plan
The detailed catalog view below loads this exact record, its source evidence, and the full seven-phase agentic change plan.