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CVE-2026-55850— Element Web: A malicious homeserver can inject HTML in Element Web using its homepage

Quick assessment

Affected
element-hq element-web
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.

Element是Element公司开源的一个 Matrix 网络协作客户端。 Element 1.12.22之前版本存在跨站脚本漏洞，该漏洞源于通过dangerouslySetInnerHTML渲染homeserver提供的首页内容时未经过sanitizedHtmlNode清理，恶意homeserver可提供特制HTML，导致内容安全策略无法阻止钓鱼HTML。

CVSS 5.3 · Medium EPSS 0.55% · P45

Possible ATT&CK Techniques 1 AI

T1189 · Drive-by Compromise

Affected Version Matrix 1

VendorProduct Version RangeStatus
element-hq element-web < 1.12.22 affected
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I. Basic Information for CVE-2026-55850

Vulnerability Information
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Vulnerability Title
Element Web: A malicious homeserver can inject HTML in Element Web using its homepage
Source: CVE Program / CVE List V5
Vulnerability Description
Element Web is a Matrix web client built using the Matrix React SDK. Prior to 1.12.22, EmbeddedPage in apps/web/src/components/structures/EmbeddedPage.tsx renders homeserver-supplied homepage content through dangerouslySetInnerHTML without passing it through sanitizedHtmlNode. A malicious homeserver can provide crafted HTML that Element Web renders on the homepage; the content security policy prevents JavaScript but not phishing HTML. This issue is fixed in version 1.12.22.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
在Web页面生成时对输入的转义处理不恰当(跨站脚本)
Source: CVE Program / CVE List V5
Vulnerability Title
Element 跨站脚本漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Element是Element公司开源的一个 Matrix 网络协作客户端。 Element 1.12.22之前版本存在跨站脚本漏洞，该漏洞源于通过dangerouslySetInnerHTML渲染homeserver提供的首页内容时未经过sanitizedHtmlNode清理，恶意homeserver可提供特制HTML，导致内容安全策略无法阻止钓鱼HTML。
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
element-hq element-web < 1.12.22 -

II. Public POCs for CVE-2026-55850

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III. Intelligence Information for CVE-2026-55850

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Patches & Fixes for CVE-2026-55850 (1)

Vendor Advisories for CVE-2026-55850 (1)

Vendor Pages for CVE-2026-55850 (1)

Other References for CVE-2026-55850 (1)

IV. Related Vulnerabilities

Same product: element-web
Same vendor: element-hq
Same weakness: CWE-79

V. Comments for CVE-2026-55850

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