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CVE-2025-66512— Nextcloud Server vulnerable to XSS in SVG images when opened outside of Nextcloud

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 Server是Nextcloud开源的一个Nextcloud服务器程序。 Nextcloud Server 31.0.12之前版本和32.0.3之前版本存在安全漏洞，该漏洞源于清理不足，可能导致内容安全策略被绕过。

CVSS 5.4 · Medium EPSS 0.28% · P18
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I. Basic Information for CVE-2025-66512

Vulnerability Information
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Vulnerability Title
Nextcloud Server vulnerable to XSS in SVG images when opened outside of Nextcloud
Source: CVE Program / CVE List V5
Vulnerability Description
Nextcloud Server is a self hosted personal cloud system. In Nextcloud Server and Server Enterprise prior to 31.0.12 and 32.0.3, a missing sanitization allowed malicious users to circumvent the content security policy when a malicious user manages to trick a user it viewing an uploaded SVG outside of the Nextcloud Servers web page.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:L
Source: CVE Program / CVE List V5
Vulnerability Type
Web页面中脚本相关HTML标签转义处理不恰当(基本跨站脚本)
Source: CVE Program / CVE List V5
Vulnerability Title
Nextcloud Server 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Nextcloud Server是Nextcloud开源的一个Nextcloud服务器程序。 Nextcloud Server 31.0.12之前版本和32.0.3之前版本存在安全漏洞，该漏洞源于清理不足，可能导致内容安全策略被绕过。
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 >= 32.0.0beta1, < 32.0.3 -

II. Public POCs for CVE-2025-66512

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III. Intelligence Information for CVE-2025-66512

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Same Patch Batch · nextcloud · 2025-12-05 · 19 CVEs total

CVE-2025-66551 6.3 MEDIUM Nextcloud Tables is missing an ownership check which allows moving columns into tables of
CVE-2025-66550 5.7 MEDIUM Nextcloud Calendar attachments of local files are offered to downloaded
CVE-2025-66557 5.4 MEDIUM Nextcloud Deck app allowed user with "Can share" permission to modify permissions of other
CVE-2025-66511 4.8 MEDIUM Nextcloud Calendar app used predictable proposal participant tokens
CVE-2025-66510 4.5 MEDIUM Nextcloud Server Contacts Search allowed users to retrieve contact information of other us
CVE-2025-66553 4.3 MEDIUM Nextcloud Tables app allowed users to view columns metadata information of any table
CVE-2025-66547 4.3 MEDIUM Nextcloud Server users can modify tags on files that do not belong to them
CVE-2025-66552 4.3 MEDIUM Nextcloud Server admin_audit does not log all actions on files in groupfolders
CVE-2025-66513 4.3 MEDIUM Nextcloud Tables app share information not limited to relevant users
CVE-2025-66514 3.5 LOW Nextcloud Mail stored HTML injection in subject text
CVE-2025-66545 3.5 LOW Nextcloud Groupfolders users with read-only permissions for team folder can restore delete
CVE-2025-66554 3.5 LOW Nextcloud Contacts vulnerable to Stored XSS in contacts app via organisation and title fie
CVE-2025-66556 3.5 LOW Nextcloud talk allows participants to blindly delete poll drafts of other users by ID
CVE-2025-66548 3.3 LOW Nextcloud Deck app allows to spoof file extensions by using RTLO characters
CVE-2025-66546 3.3 LOW Nextcloud Calendar app allowed booking appointments without the generated token
CVE-2025-66558 3.1 LOW Nextcloud Twofactor WebAuthn app was updated based on public key
CVE-2025-66515 2.7 LOW Nextcloud Approval app allows users to request approval for other users file
CVE-2025-66549 2.4 LOW Nextcloud Desktop discloses information when attempting to lock a file inside a end-to-end

IV. Related Vulnerabilities

Same product: security-advisories
Same vendor: nextcloud
Same weakness: CWE-80

V. Comments for CVE-2025-66512

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