What’s Vulnerable › Vulnerabilities

CVE-2021-41177: Rate-limits not working on instances without configured memory cache backend

• Severity: high (CVSS 8.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.6% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-10-25 · updated 2026-06-17
• Weakness: CWE-799

Description

Nextcloud is an open-source, self-hosted productivity platform. Prior to versions 20.0.13, 21.0.5, and 22.2.0, Nextcloud Server did not implement a database backend for rate-limiting purposes. Any component of Nextcloud using rate-limits (as as `AnonRateThrottle` or `UserRateThrottle`) was thus not rate limited on instances not having a memory cache backend configured. In the case of a default installation, this would notably include the rate-limits on the two factor codes. It is recommended that the Nextcloud Server be upgraded to 20.0.13, 21.0.5, or 22.2.0. As a workaround, enable a memory cache backend in `config.php`.

Affected products

• Nextcloud Server: before 20.0.13; from 21.0.0 before 21.0.5; from 22.0.0 before 22.2.0 — fixed in 20.0.13, 21.0.5, 22.2.0

How to fix

Upgrade to a fixed version: Nextcloud Server 20.0.13, 21.0.5, 22.2.0. Check the vendor advisory for mitigations.

References

• https://github.com/nextcloud/security-advisories/security/advisories/GHSA-fj39-4qx4-m3f2
• https://github.com/nextcloud/server/pull/28728
• https://hackerone.com/reports/1265709
• https://security.gentoo.org/glsa/202208-17
• https://github.com/nextcloud/security-advisories/security/advisories/GHSA-fj39-4qx4-m3f2
• https://github.com/nextcloud/server/pull/28728
• https://hackerone.com/reports/1265709
• https://security.gentoo.org/glsa/202208-17

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