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.
- 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
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
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 | 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 include 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.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
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 Symfony UX: Format-less date LiveProps parsed with the permissive DateTime constructor
- CVE-2026-49211 Symfony UX: Information exposure via unescaped LIKE wildcards in EntitySearchUtil
- CVE-2026-49212 Symfony UX: LiveComponentHydrator HMAC checksum lacks component and slot binding
- CVE-2026-55877 Symfony UX: XSS in symfony/ux-icons via unsanitized SVG content in local files and Iconify on-demand responses
- CVE-2026-49209 Symfony UX: Denial of service in symfony/ux-live-component via unbounded batch action requests
Sources
Also known as GHSA-38x5-rcv4-xf7x.