Description
Nextcloud Server 30.0.0 is vulnerable to an Insecure Direct Object Reference (IDOR) in the /core/preview endpoint. Any authenticated user can access previews of arbitrary files belonging to other users by manipulating the fileId parameter. This allows unauthorized disclosure of sensitive data, such as text files or images, without prior sharing permissions.
Affected products
nextcloud: nextcloud server
References3
- drive.google.com/file/d/1eD3PN-u1caZYgGH96XHmJ7h_OBXEAHW4/view?… Exploit
- gist.github.com/tarekramm/586dfe2d113fedfee6d71182570fc090 ExploitThird Party Advisory
- nextcloud.com Product
Metrics
- CVSS 3.1
-
4.3
MEDIUM
Score source: CNA
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N - EPSS — exploit probability
- 0% percentile: 26 · as of 11 November 2026
- CWE
- CWE-639
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.