Description
Nextcloud Server is a Nextcloud package that handles data storage. Nextcloud Server supports application specific tokens for authentication purposes. These tokens are supposed to be granted to a specific applications (e.g. DAV sync clients), and can also be configured by the user to not have any filesystem access. Due to a lacking permission check, the tokens were able to change their own permissions in versions prior to 19.0.13, 20.0.11, and 21.0.3. Thus fileystem limited tokens were able to grant themselves access to the filesystem. The issue is patched in versions 19.0.13, 20.0.11, and 21.0.3. There are no known workarounds aside from upgrading.
CVSS breakdown
CVSS 3.1
Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High
Affected products
- nextcloud / security-advisories< 19.0.13 – < 19.0.13
- nextcloud / security-advisories>= 20.0.0, < 20.0.11 – >= 20.0.0, < 20.0.11
- nextcloud / security-advisories>= 21.0.0, < 21.0.3 – >= 21.0.0, < 21.0.3
References
- VENDOR_ADVISORYhttps://github.com/nextcloud/security-advisories/security/advisories/GHSA-48m7-7r2r-838r
- PATCHhttps://github.com/nextcloud/server/pull/27000
- MISChttps://hackerone.com/reports/1193321
- MAILING_LISThttps://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/J63NBVPR2AQCAWRNDOZSGRY5II4WS2CZ/
- MAILING_LISThttps://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BVZS26RDME2DYTKET5AECRIZDFUGR2AZ/
- MISChttps://security.gentoo.org/glsa/202208-17