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CVE-2021-32802— Preview generation used third-party library not suited for user-generated content in Nextcloud server

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Nextcloud 服务器调用了不可信内容的第三方库。

CVSS 9.3 · Critical EPSS 2.60% · P85

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application
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I. Basic Information for CVE-2021-32802

Vulnerability Information
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Vulnerability Title
Preview generation used third-party library not suited for user-generated content in Nextcloud server
Source: CVE Program / CVE List V5
Vulnerability Description
Nextcloud server is an open source, self hosted personal cloud. Nextcloud supports rendering image previews for user provided file content. For some image types, the Nextcloud server was invoking a third-party library that wasn't suited for untrusted user-supplied content. There are several security concerns with passing user-generated content to this library, such as Server-Side-Request-Forgery, file disclosure or potentially executing code on the system. The risk depends on your system configuration and the installed library version. It is recommended that the Nextcloud Server is upgraded to 20.0.12, 21.0.4 or 22.1.0. These versions do not use this library anymore. As a workaround users may disable previews by setting `enable_previews` to `false` in `config.php`.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:L
Source: CVE Program / CVE List V5
Vulnerability Type
从非可信控制范围包含功能例程
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Nextcloud 服务器调用了不可信内容的第三方库。
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-2021-32802

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III. Intelligence Information for CVE-2021-32802

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Vendor Advisories for CVE-2021-32802 (2)

Other References for CVE-2021-32802 (1)

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

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-2021-32766 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-829

V. Comments for CVE-2021-32802

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