CVE-2026-49209 Symfony UX: Denial of service in symfony/ux-live-component via unbounded batch action requests
An authenticated attacker can cause denial of service by submitting unbounded batch action requests, exhausting server resources.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-49209?
CVE-2026-49209 is a medium-severity denial of service vulnerability in symfony ux, published on 17 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
Symfony UX is a JavaScript ecosystem for Symfony. From 2.5.0 until 2.36.0 and 3.1.0, Symfony\UX\LiveComponent\Controller\BatchActionController::__invoke() iterates over the client-supplied actions array and issues a full HttpKernel sub-request for each entry; because the array size is never bounded, an authenticated client can submit a single _batch request containing thousands of actions and exhaust CPU, memory, and database connections on the application server. This issue is fixed in versions 2.36.0 and 3.1.0.
Weakness: CWE-770
Which versions are affected by CVE-2026-49209?
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 2.5.0 | 2.36.0 |
symfony/ux-live-component Packagist | From 2.5.0 | 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-2026-49209?
Upgrade symfony/ux-live-component to a fixed version for your release line: 2.36.0 or 3.1.0.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-49209 being exploited?
There is no known exploitation of CVE-2026-49209 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-2026-49216 Symfony UX: XSS in symfony/ux-autocomplete via unescaped AJAX response data
Sources
Also known as GHSA-mm82-c99c-h2cf.