What’s Vulnerable › Vulnerabilities

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

• Severity: medium (CVSS 6.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-07-17 · updated 2026-10-24
• Weakness: CWE-79

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.

Affected products

• symfony ux: from 2.8.0 before 2.36.0; 3.0.0 — fixed in 2.36.0

How to fix

Upgrade to a fixed version: symfony ux 2.36.0. Check the vendor advisory for mitigations.

References

• 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
• https://github.com/symfony/ux/security/advisories/GHSA-38x5-rcv4-xf7x

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