CVE-2026-55850

Element Web: A malicious homeserver can inject HTML in Element Web using its homepage

MEDIUM
5.3
CVSS Score
Published: August 21, 2026 at 06:30 PM UTC
Updated: October 14, 2026 at 07:10 PM UTC
1 product affected across 1 vendorElement Web

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Severity
MEDIUM5.3
Exploit prediction
EPSS 0.5%
SSVC
No known exploit

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 1.12.22
Affected range stops below 1.12.22, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet, and no fixed version or vendor advisory is recorded against it.

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

5.3MEDIUMGitHub_M
Vector?

Quick Info

StatusDEFERRED
CWE
CWE-79

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