title: Preview generation used third-party library not suited for user-generated content in Nextcloud server
description: Nextcloud server is an open source, self hosted personal cloud. Nextcloud supports rendering image previews for user provided file content. For some image types, the Nextcloud server was invoking a third-party library that wasn't suited for untrusted user-supplied content. There are several security concerns with passing user-generated content to this library, such as Server-Side-Request-Forgery, file disclosure or potentially executing code on the system. The risk depends on your system configuration and the installed library version. It is recommended that the Nextcloud Server is upgraded to 20.0.12, 21.0.4 or 22.1.0. These versions do not use this library anymore. As a workaround users may disable previews by setting `enable_previews` to `false` in `config.php`.
problem types: CWE-829: Inclusion of Functionality from Untrusted Control Sphere
affected:
{
product: security-advisories
vendor: nextcloud
versions:
status: affected, version: < 20.0.12
status: affected, version: >= 21.0.0, < 21.0.4
status: affected, version: >= 22.0.0, < 22.1.0
}
metrics:
cvssV3_1: [
attackComplexity: LOW
attackVector: NETWORK
availabilityImpact: LOW
baseScore: 9.3
baseSeverity: CRITICAL
confidentialityImpact: HIGH
integrityImpact: NONE
privilegesRequired: NONE
scope: CHANGED
userInteraction: NONE
vectorString: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:L
version: 3.1
]