Auth bypass in Nextcloud Server
CVE-2021-41241
Nextcloud server is a self hosted system designed to provide cloud style services. The groupfolders application for Nextcloud allows sharing a folder with a group of people. In addition, it allows setting "advanced permissions" on subfolders, for example, a user could be granted access to the groupfolder but not specific subfolders. Due to a lacking permission check in affected versions, a user could still access these subfolders by copying the groupfolder to another location. It is recommended that the Nextcloud Server is upgraded to 20.0.14, 21.0.6 or 22.2.1. Users unable to upgrade should disable the "groupfolders" application in the admin settings.
Vulnerability class: Broken Access Control
EPSS: 0.009 (54.4th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 4.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N.
Affected products
- Nextcloud Nextcloud_server — versions 22.2.0
- Nextcloud Security-advisories — versions < 20.0.14, >= 21.0.0, < 21.0.6, >= 22.2.0, < 22.2.1
Weakness classification (CWE)
Public proof-of-concept exploits
References
- security-advisories@github.com (x_refsource_CONFIRM, Third Party Advisory, Issue Tracking)
- security-advisories@github.com (Patch, Third Party Advisory, x_refsource_MISC, Issue Tracking)
- security-advisories@github.com (Patch, Third Party Advisory, x_refsource_MISC)
- security-advisories@github.com (vendor-advisory, Third Party Advisory, x_refsource_GENTOO)
Frequently asked questions
- What is CVE-2021-41241?
- CVE-2021-41241 is a medium-severity vulnerability in Nextcloud Server, classified under Incorrect Authorization. CVSS score: 4.3/10. Published 2022-03-08.
- How severe is CVE-2021-41241?
- Medium severity. CVSS v3 base score is 4.3 out of 10.
- Is CVE-2021-41241 known to be exploited?
- 2 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.