title: Attacker can obtain write access to any federated share/public link
description: Nextcloud Server is a Nextcloud package that handles data storage. In versions prior to 19.0.11, 20.0.10, and 21.0.2, an attacker is able to receive write/read privileges on any Federated File Share. Since public links can be added as federated file share, this can also be exploited on any public link. Users can upgrade to patched versions (19.0.11, 20.0.10 or 21.0.2) or, as a workaround, disable federated file sharing.
problem types: CWE-639: Authorization Bypass Through User-Controlled Key
affected:
{
product: security-advisories
vendor: nextcloud
versions:
status: affected, version: < 19.0.11
status: affected, version: >= 20.0.0, < 20.0.10
status: affected, version: >= 21.0.0, < 21.0.2
}
metrics:
cvssV3_1: [
attackComplexity: HIGH
attackVector: NETWORK
availabilityImpact: HIGH
baseScore: 8.1
baseSeverity: HIGH
confidentialityImpact: HIGH
integrityImpact: HIGH
privilegesRequired: NONE
scope: UNCHANGED
userInteraction: NONE
vectorString: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
version: 3.1
]