# 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.

- **Severity:** Medium 5.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 17 Jul 2026
- **Updated:** 17 Jul 2026
- **Also known as:** GHSA-mm82-c99c-h2cf

## 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 (Allocation of Resources Without Limits or Throttling)

## 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 | Ecosystem | 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: 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.

## 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](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-2026-49216](https://insights.sbomify.com/CVE-2026-49216/): Symfony UX: XSS in symfony/ux-autocomplete via unescaped AJAX response data (medium 5.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-49209 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-49209 in the wild and no public exploit code.

Affected packages and fixed versions:
- symfony/ux-live-component (Packagist): affected from 2.5.0; fixed in 2.36.0
- symfony/ux-live-component (Packagist): affected from 2.5.0; 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-2026-49209/ (Markdown: https://insights.sbomify.com/CVE-2026-49209/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-49209
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-49209
- OSV: https://osv.dev/vulnerability/CVE-2026-49209

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-49209/
Summaries are generated and may contain mistakes; the official description above is the record.