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CVE-2021-37631— Circle can be accessed by non-Circle members in Nextcloud Deck

Quick assessment

Affected
nextcloud security-advisories
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Nextcloud是德国Nextcloud公司的一套开源的自托管文件同步和共享的通信应用平台。 Nextcloud存在安全漏洞，该漏洞源于Deck应用程序没有正确地检查Circle中的用户成员。这允许实例中的其他用户访问已与Circle共享的面板内容，即使该用户不是该Circle的成员。

CVSS 6.5 · Medium EPSS 1.28% · P69

Possible ATT&CK Techniques 1 AI

T1528 · Steal Application Access Token
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I. Basic Information for CVE-2021-37631

Vulnerability Information
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Vulnerability Title
Circle can be accessed by non-Circle members in Nextcloud Deck
Source: CVE Program / CVE List V5
Vulnerability Description
Deck is an open source kanban style organization tool aimed at personal planning and project organization for teams integrated with Nextcloud. In affected versions the Deck application didn't properly check membership of users in a Circle. This allowed other users in the instance to gain access to boards that have been shared with a Circle, even if the user was not a member of the circle. It is recommended that Nextcloud Deck is upgraded to 1.5.1, 1.4.4 or 1.2.9. If you are unable to update it is advised to disable the Deck plugin.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
通过用户控制密钥绕过授权机制
Source: CVE Program / CVE List V5
Vulnerability Title
Nextcloud安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Nextcloud是德国Nextcloud公司的一套开源的自托管文件同步和共享的通信应用平台。 Nextcloud存在安全漏洞，该漏洞源于Deck应用程序没有正确地检查Circle中的用户成员。这允许实例中的其他用户访问已与Circle共享的面板内容，即使该用户不是该Circle的成员。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
nextcloud security-advisories < 1.2.9 -

II. Public POCs for CVE-2021-37631

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III. Intelligence Information for CVE-2021-37631

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Patches & Fixes for CVE-2021-37631 (1)

Vendor Advisories for CVE-2021-37631 (1)

Other References for CVE-2021-37631 (2)

Same Patch Batch · nextcloud · 2021-09-07 · 9 CVEs total

CVE-2021-32802 9.3 CRITICAL Preview generation used third-party library not suited for user-generated content in Nextc
CVE-2021-32800 8.1 HIGH Bypass of Two Factor Authentication in Nextcloud server
CVE-2021-37628 7.5 HIGH File Drop can be bypassed using Richdocuments app in nextcloud
CVE-2021-37630 6.5 MEDIUM Secret Circle can be joined without approval in Nextcloud Circles
CVE-2021-32782 5.8 MEDIUM Cross-Site Scripting in Nextcloud Circles
CVE-2021-32801 5.5 MEDIUM Exceptions may have logged Encryption-at-Rest key content in Nextcloud server
CVE-2021-32766 5.3 MEDIUM Nextcloud Text app can disclose existence of folders in "File Drop" link share
CVE-2021-37629 5.3 MEDIUM Lack of ratelimit on Richdocuments OCS endpoint in nextcloud

IV. Related Vulnerabilities

Same product: security-advisories
Same vendor: nextcloud
Same weakness: CWE-639

V. Comments for CVE-2021-37631

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