title: Nextcloud Server users can make external storage mount points inaccessible for other users
description: Nextcloud Server provides data storage for Nextcloud, an open source cloud platform. Starting in version 25.0.0 and prior to versions 25.0.13, 26.0.8, and 27.1.3 of Nextcloud Server and starting in version 20.0.0 and prior to versions 20.0.14.16, 21.0.9.13, 22.2.10.15, 23.0.12.12, 24.0.12.8, 25.0.13, 26.0.8, and 27.1.3 of Nextcloud Enterprise Server, a malicious user could update any personal or global external storage, making them inaccessible for everyone else as well. Nextcloud Server 25.0.13, 26.0.8, and 27.1.3 and Nextcloud Enterprise Server is upgraded to 20.0.14.16, 21.0.9.13, 22.2.10.15, 23.0.12.12, 24.0.12.8, 25.0.13, 26.0.8, and 27.1.3 contain a patch for this issue. As a workaround, disable app files_external. This workaround also makes the external storage inaccessible but retains the configurations until a patched version has been deployed.
problem types: CWE-284: Improper Access Control
affected:
{
vendor: nextcloud
product: security-advisories
versions:
version: >= 25.0.0, < 25.0.13, status: affected
version: >= 26.0.0, < 26.0.8, status: affected
version: >= 27.0.0, < 27.1.3, status: affected
version: >= 20.0.0, < 20.0.14.16, status: affected
version: >= 21.0.0, < 21.0.9.13, status: affected
version: >= 22.0.0, < 22.2.10.15, status: affected
version: >= 23.0.0, < 23.0.12.12, status: affected
version: >= 24.0.0, < 24.0.12.8, status: affected
}
metrics:
cvssV3_1: [
attackComplexity: LOW
attackVector: NETWORK
availabilityImpact: HIGH
baseScore: 8.5
baseSeverity: HIGH
confidentialityImpact: NONE
integrityImpact: LOW
privilegesRequired: LOW
scope: CHANGED
userInteraction: NONE
vectorString: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:L/A:H
version: 3.1
]