Nextcloud Server 30.0.0 is vulnerable to an Insecure Direct Object Reference (IDOR) in the /core/preview endpoint.

published 2025-12-12 10 mo ago modified 2026-10-14 25 d ago also EUVD-2025-203106

cvss: 4.3; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.3%; EPSS 0.3% chance of exploitation in 30 days, percentile 25%
public exploits: 0; none known

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.

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: partial
Assessed: 10 mo ago (2025-12-12)

Exploit prediction

0.32% chance of exploitation in the next 30 days, higher than 25% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

drive.google.com https://drive.google.com/file/d/1eD3PN-u1caZYgGH96XHmJ7h_OBXEAHW4/view?usp=sharing referenced PoC, tagged "exploit" by a source, unverified
gist.github.com https://gist.github.com/tarekramm/586dfe2d113fedfee6d71182570fc090 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
CISA ADP	3.1	4.3	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
CNA	3.1	4.3	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

Classification

Weakness

CWE-639 Authorization Bypass Through User-Controlled Key

References

drive.google.com /file/d/1eD3PN-u1caZYgGH96XHmJ7h_OBXEAHW4/view?usp=sharing
exploit
gist.github.com /tarekramm/586dfe2d113fedfee6d71182570fc090
exploit, third-party-advisory
nextcloud.com
product

Sources

CVE List CVE-2025-64011
NVD CVE-2025-64011

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary