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CVE-2021-32766— Nextcloud Text app can disclose existence of folders in "File Drop" link share

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 Text 存在安全漏洞，该漏洞源于在受影响的版本中，Nextcloud Text 应用程序返回不同的错误消息，具体取决于公共链接共享中是否存在文件夹。如果公共链接共享是使用“仅上传”权限创建的，则这是有问题的。 （又名“文件删除”）。链接共享收件人不会看到“文件放置”共享中存在哪些文件夹或文件。使用此漏洞，攻击者能够枚举此类共享中的文件夹。漏洞利用要求攻击者有权访问有效的受影响的“文件删除”

CVSS 5.3 · Medium EPSS 1.34% · P70

Possible ATT&CK Techniques 1 AI

T1083 · File and Directory Discovery
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I. Basic Information for CVE-2021-32766

Vulnerability Information
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Vulnerability Title
Nextcloud Text app can disclose existence of folders in "File Drop" link share
Source: CVE Program / CVE List V5
Vulnerability Description
Nextcloud Text is an open source plaintext editing application which ships with the nextcloud server. In affected versions the Nextcloud Text application returned different error messages depending on whether a folder existed in a public link share. This is problematic in case the public link share has been created with "Upload Only" privileges. (aka "File Drop"). A link share recipient is not expected to see which folders or files exist in a "File Drop" share. Using this vulnerability an attacker is able to enumerate folders in such a share. Exploitation requires that the attacker has access to a valid affected "File Drop" link share. It is recommended that the Nextcloud Server is upgraded to 20.0.12, 21.0.4 or 22.0.1. Users who are unable to upgrade are advised to disable the Nextcloud Text application in the app settings.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
通过错误消息导致的信息暴露
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 Text 存在安全漏洞，该漏洞源于在受影响的版本中，Nextcloud Text 应用程序返回不同的错误消息，具体取决于公共链接共享中是否存在文件夹。如果公共链接共享是使用“仅上传”权限创建的，则这是有问题的。 （又名“文件删除”）。链接共享收件人不会看到“文件放置”共享中存在哪些文件夹或文件。使用此漏洞，攻击者能够枚举此类共享中的文件夹。漏洞利用要求攻击者有权访问有效的受影响的“文件删除”
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 < 20.0.12 -

II. Public POCs for CVE-2021-32766

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III. Intelligence Information for CVE-2021-32766

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Patches & Fixes for CVE-2021-32766 (1)

Vendor Advisories for CVE-2021-32766 (1)

Other References for CVE-2021-32766 (1)

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-2021-37631 6.5 MEDIUM Circle can be accessed by non-Circle members in Nextcloud Deck
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-2021-37629 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-209

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