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Date: June 1, 2021

Nextcloud Server is a Nextcloud package that handles data storage. A vulnerability in federated share exists in versions prior to 19.0.11, 20.0.10, and 21.0.2. An attacker can gain access to basic information about users of a server by accessing a public link that a legitimate server user added as a federated share. This happens because Nextcloud supports sharing registered users with other Nextcloud servers, which can be done automatically when selecting the "Add server automatically once a federated share was created successfully" setting. The vulnerability is patched in versions 19.0.11, 20.0.10, and 21.0.2 As a workaround, disable "Add server automatically once a federated share was created successfully" in the Nextcloud settings.

Language: PHP

Severity Score

Severity Score

Weakness Type (CWE)

Improper Access Control


Top Fix


Upgrade Version

Upgrade to version v19.0.11,v20.0.10, v21.0.2

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CVSS v3.1

Base Score:
Attack Vector (AV): NETWORK
Attack Complexity (AC): LOW
Privileges Required (PR): NONE
User Interaction (UI): NONE
Scope (S): CHANGED
Confidentiality (C): HIGH
Integrity (I): NONE
Availability (A): NONE


Base Score:
Access Vector (AV): NETWORK
Access Complexity (AC): LOW
Authentication (AU): NONE
Confidentiality (C): PARTIAL
Integrity (I): NONE
Availability (A): NONE
Additional information:

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