CVE-2026-49209: symfony/ux-live-component Denial of Service Vulnerability

LOW
Advisory Identifier: GHSA-mm82-c99c-h2cf
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CWE-770
Published
Advisory Summary

CVE-2026-49209 is a LOW denial of service vulnerability (CWE-770: Allocation of Resources Without Limits or Throttling) affecting symfony/ux-live-component libraries in the Packagist ecosystem. The issue involves denial of service via unbounded batch action requests. Remediation is available by upgrading affected packages to version 2.36.0, 3.1.0.

CVE-2026-49209 at a Glance

CVE Identifier CVE-2026-49209
GHSA Identifier GHSA-mm82-c99c-h2cf
Severity LOW
CVSS v3.1 Base Score N/A
CWE Classification CWE-770: Allocation of Resources Without Limits or Throttling
Affected Product symfony/ux-live-component
Package Ecosystem Packagist
Published Date
Last Updated

How to Fix CVE-2026-49209

To remediate this vulnerability, upgrade all affected symfony/ux-live-component dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

symfony/ux-live-component fixed: 2.36.0 
Upgrade symfony/ux-live-component to 2.36.0
symfony/ux-live-component fixed: 3.1.0 
Upgrade symfony/ux-live-component to 3.1.0
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for symfony/ux-live-component

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-49209, inspect your project dependencies for symfony/ux-live-component:

inspect dependencies for symfony/ux-live-component

Analyze the terminal output to locate any version of symfony/ux-live-component in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 2.36.0), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-770: Allocation of Resources Without Limits or Throttling, where the product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated. In symfony/ux-live-component, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Description `Symfony\UX\LiveComponent\Controller\BatchActionController::__invoke()` iterates over the client-supplied `actions` array and issues a full `HttpKernel` sub-request for each entry (event subscribers, validators, Doctrine, rendering). The array size is never bounded, so an authenticated client can submit a single `_batch` request containing thousands of actions and exhaust CPU, memory, and database connections on the application server. ### Resolution `BatchActionController` now enforces an upper bound of 50 actions per `_batch` request (`MAX_ACTIONS_PER_BATCH`) and rejects larger payloads up front with a `BadRequestHttpException`. The matching JavaScript backend was also updated to split larger client-side batches into multiple requests so legitimate usage isn't affected. The patch for this issue is available [here](https://github.com/symfony/ux/commit/95e878d5257f13d6d652ca95e3ef6bb0934d674f) for branch 2.x (and forward-ported to 3.x). ### Credits Symfony would like to thank Pascal Cescon for reporting the issue and Hugo Alliaume for providing the fix.

CVE-2026-49209 Affected symfony/ux-live-component Versions

2 component(s)
Fixed Versions:
2.36.03.1.0
Product / Package Ecosystem Affected Versions Fixed Version
symfony/ux-live-component
 Packagist
≥ 2.5.0
< 2.36.0
2.36.0
symfony/ux-live-component
 Packagist
≥ 3.0.0
< 3.1.0
3.1.0

References

GitHub Advisory / Wiki ADVISORY
https://github.com/symfony/ux/security/advisories/GHSA-mm82-c99c-h2cf
Security Fix Commit FIX COMMIT
https://github.com/symfony/ux/commit/95e878d5257f13d6d652ca95e3ef6bb0934d674f
symfony/ux-live-component Source Repository REPOSITORY
https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/ux-live-component/CVE-2026-49209.yaml
symfony/ux-live-component Source Repository REPOSITORY
https://github.com/symfony/ux

Frequently Asked Questions

What is CVE-2026-49209?
CVE-2026-49209 is a security vulnerability in symfony/ux-live-component involving Denial of service via unbounded batch action requests under CWE-770: Allocation of Resources Without Limits or Throttling.
Which symfony/ux-live-component versions are affected?
Affected versions include releases prior to 2.36.0, 3.1.0 across affected packages: symfony/ux-live-component.
What version fixes CVE-2026-49209?
Upgrading to 2.36.0, 3.1.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is symfony/ux-live-component affected?
Yes, symfony/ux-live-component is affected in releases prior to 2.36.0, 3.1.0. Upgrade your dependency to 2.36.0, 3.1.0 or later.
What CWE is associated with CVE-2026-49209?
CVE-2026-49209 is classified under CWE-770: Allocation of Resources Without Limits or Throttling (The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.).
How can I check Packagist dependencies for CVE-2026-49209?
Run the dependency tree command: 'inspect dependencies for symfony/ux-live-component'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-mm82-c99c-h2cf",
  "modified" : "2026-06-19T19:34:45Z",
  "published" : "2026-06-19T19:34:45Z",
  "aliases" : [ "CVE-2026-49209" ],
  "summary" : "symfony/ux-live-component: Denial of service via unbounded batch action requests",
  "details" : "### Description\n\n`Symfony\\UX\\LiveComponent\\Controller\\BatchActionController::__invoke()` iterates over the client-supplied `actions` array and issues a full `HttpKernel` sub-request for each entry (event subscribers, validators, Doctrine, rendering). The array size is never bounded, so an authenticated client can submit a single `_batch` request containing thousands of actions and exhaust CPU, memory, and database connections on the application server.\n\n### Resolution\n\n`BatchActionController` now enforces an upper bound of 50 actions per `_batch` request (`MAX_ACTIONS_PER_BATCH`) and rejects larger payloads up front with a `BadRequestHttpException`. The matching JavaScript backend was also updated to split larger client-side batches into multiple requests so legitimate usage isn't affected.\n\nThe patch for this issue is available [here](https://github.com/symfony/ux/commit/95e878d5257f13d6d652ca95e3ef6bb0934d674f) for branch 2.x (and forward-ported to 3.x).\n\n### Credits\n\nSymfony would like to thank Pascal Cescon for reporting the issue and Hugo Alliaume for providing the fix.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "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/E:U"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "symfony/ux-live-component"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "2.5.0"
      }, {
        "fixed" : "2.36.0"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "symfony/ux-live-component"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "3.0.0"
      }, {
        "fixed" : "3.1.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/symfony/ux/security/advisories/GHSA-mm82-c99c-h2cf"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/symfony/ux/commit/95e878d5257f13d6d652ca95e3ef6bb0934d674f"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/ux-live-component/CVE-2026-49209.yaml"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/symfony/ux"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-770" ],
    "severity" : "LOW",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-06-19T19:34:45Z",
    "nvd_published_at" : null
  }
}