CVE-2025-66510: Nextcloud Server Contacts Search allowed users to retrieve contact information of other users beyond their contact list

Severity: medium (CVSS 4.9 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-12-05 · updated 2026-10-18
Weakness: CWE-359

Description

Nextcloud Server is a self hosted personal cloud system. In Nextcloud Server prior to 31.0.10 and 32.0.1 and Nextcloud Enterprise Server prior to 28.0.14.11, 29.0.16.8, 30.0.17.3, and 31.0.10, contacts search allowed to retrieve personal data of other users (emails, names, identifiers) without proper access control. This allows an authenticated user to retrieve information about accounts that are not related or added as contacts.

Affected products

Nextcloud Server: from 28.0.0 before 28.0.14.11; from 29.0.0 before 29.0.16.8; from 30.0.0 before 30.0.17.3; from 31.0.0 before 31.0.10; from 32.0.0 before 32.0.1 — fixed in 28.0.14.11, 29.0.16.8, 30.0.17.3, 31.0.10, 32.0.1

How to fix

Upgrade to a fixed version: Nextcloud Server 28.0.14.11, 29.0.16.8, 30.0.17.3, 31.0.10. Check the vendor advisory for mitigations.

References

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