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

> An attacker can inject arbitrary HTML and scripts via child component tags in Symfony UX Live Components, leading to cross-site scripting.

- **Severity:** Low 2.3 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 17 Jul 2026
- **Updated:** 17 Jul 2026
- **Also known as:** GHSA-38x5-rcv4-xf7x

## What is CVE-2026-49210?

CVE-2026-49210 is a low-severity cross-site scripting vulnerability in symfony ux, published on 17 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official 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.

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2026-49210?

4 open source packages ship an affected version, including symfony/ux-live-component. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `symfony/ux-live-component` | Packagist | From 2.8.0 | 2.36.0 |
| `symfony/ux-live-component` | Packagist | From 2.8.0 | 2.36.0 |
| `symfony/ux-live-component` | Packagist | From 3.0.0 | 3.1.0 |
| `symfony/ux-live-component` | Packagist | From 3.0.0 | 3.1.0 |

Products: Symfony Ux.

## How do I fix CVE-2026-49210?

Upgrade symfony/ux-live-component to a fixed version for your release line: 2.36.0 or 3.1.0.

## Is CVE-2026-49210 being exploited?

There is no known exploitation of CVE-2026-49210 in the wild and no public exploit code.

## Other vulnerabilities in symfony ux

- [CVE-2026-49208](https://insights.sbomify.com/CVE-2026-49208/): Symfony UX: Format-less date LiveProps parsed with the permissive DateTime constructor (medium 6.9)
- [CVE-2026-49211](https://insights.sbomify.com/CVE-2026-49211/): Symfony UX: Information exposure via unescaped LIKE wildcards in EntitySearchUtil (medium 6.9)
- [CVE-2026-49212](https://insights.sbomify.com/CVE-2026-49212/): Symfony UX: LiveComponentHydrator HMAC checksum lacks component and slot binding (medium 6.9)
- [CVE-2026-55877](https://insights.sbomify.com/CVE-2026-55877/): Symfony UX: XSS in symfony/ux-icons via unsanitized SVG content in local files and Iconify on-demand responses (medium 6.1)
- [CVE-2026-49209](https://insights.sbomify.com/CVE-2026-49209/): Symfony UX: Denial of service in symfony/ux-live-component via unbounded batch action requests (medium 5.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-49210 and fix it if it is affected.

What it is: CVE-2026-49210 is a low-severity cross-site scripting vulnerability in symfony ux, published on 17 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-49210 in the wild and no public exploit code.

Affected packages and fixed versions:
- symfony/ux-live-component (Packagist): affected from 2.8.0; fixed in 2.36.0
- symfony/ux-live-component (Packagist): affected from 2.8.0; fixed in 2.36.0
- symfony/ux-live-component (Packagist): affected from 3.0.0; fixed in 3.1.0
- symfony/ux-live-component (Packagist): affected from 3.0.0; fixed in 3.1.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-49210/ (Markdown: https://insights.sbomify.com/CVE-2026-49210/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-49210
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-49210
- OSV: https://osv.dev/vulnerability/CVE-2026-49210

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-49210/
Summaries are generated and may contain mistakes; the official description above is the record.