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CVE-2021-32707— Bypass of image blocking in Nextcloud Mail

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 Mail在1.9.6之前的版本存在安全漏洞，该漏洞源于隐私过滤器未能过滤具有“background-image”CSS属性的图像。

CVSS 4.3 · Medium EPSS 1.15% · P66

Possible ATT&CK Techniques 1 AI

T1530 · Data from Cloud Storage
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I. Basic Information for CVE-2021-32707

Vulnerability Information
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Vulnerability Title
Bypass of image blocking in Nextcloud Mail
Source: CVE Program / CVE List V5
Vulnerability Description
Nextcloud Mail is a mail app for Nextcloud. In versions prior to 1.9.6, the Nextcloud Mail application does not, by default, render images in emails to not leak the read state. The privacy filter failed to filter images with a `background-image` CSS attribute. Note that the images were still passed through the Nextcloud image proxy, and thus there was no IP leakage. The issue was patched in version 1.9.6 and 1.10.0. No workarounds are known to exist.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
输入验证不恰当
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 Mail在1.9.6之前的版本存在安全漏洞，该漏洞源于隐私过滤器未能过滤具有“background-image”CSS属性的图像。
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 < 1.9.6 -

II. Public POCs for CVE-2021-32707

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III. Intelligence Information for CVE-2021-32707

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Patches & Fixes for CVE-2021-32707 (1)

Vendor Advisories for CVE-2021-32707 (1)

Other References for CVE-2021-32707 (1)

Same Patch Batch · nextcloud · 2021-07-12 · 14 CVEs total

CVE-2021-32688 8.8 HIGH Application specific tokens can change their own scope
CVE-2021-32689 8.1 HIGH Nextcloud Talk not properly disassociating users from chats after account deletion
CVE-2021-32726 7.1 HIGH Webauthn tokens not removed after user has been deleted
CVE-2021-32727 5.7 MEDIUM End-to-end encryption device setup did not verify public key
CVE-2021-32741 5.3 MEDIUM Lack of ratelimit on public share link mount endpoint
CVE-2021-32705 5.3 MEDIUM Lack of ratelimit on public DAV endpoint
CVE-2021-32703 5.3 MEDIUM Lack of ratelimit on shareinfo endpoint
CVE-2021-32733 4.8 MEDIUM XSS in Nextcloud Text application
CVE-2021-32678 3.7 LOW Ratelimit not applied on OCS API responses
CVE-2021-32725 3.5 LOW Default share permissions not respected for federated reshares
CVE-2021-32679 3.5 LOW Filenames not escaped by default in controllers using DownloadResponse
CVE-2021-32680 3.3 LOW Audit log is not properly logging unsetting of share expiration date
CVE-2021-32734 3.1 LOW File path disclosure of shared files in Nextcloud Text application

IV. Related Vulnerabilities

Same product: security-advisories
Same vendor: nextcloud
Same weakness: CWE-20

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