CVE-2026-49212: Symfony UX insufficient verification of data authenticity in LiveComponent

CVE-2026-49212 · Severity: medium · CVSS 4 · Published 2026-07-17

Symfony UX is a collection of tools for building interactive user interfaces in Symfony applications. A security flaw in the LiveComponent library could allow an attacker to bypass data integrity checks by reusing security tokens from one part of the application in another. This could potentially allow unauthorized changes to data fields that were intended to be read-only, affecting the integrity of the application's state.

Technologies: symfony/ux-live-component (Packagist), Symfony UX Live Component. Vendors: Packagist, Symfony.

Quick answers

Is CVE-2026-49212 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-49212 being exploited in the wild.
How severe is CVE-2026-49212?
Medium severity, with a CVSS score of 4, published 17 July 2026.
Which products and versions are affected?
symfony/ux-live-component (Packagist) ECOSYSTEM:introduced=2.8.0,fixed=2.36.0; Symfony UX >= 2.8.0, < 2.36.0; Symfony UX Live Component >= 2.8.0, < 2.36.0; >= 3.0.0, < 3.1.0.
Is there a fix for CVE-2026-49212?
Yes. symfony/ux-live-component (Packagist): upgrade to 2.36.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-49212 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-49212?
Check whether you run symfony/ux-live-component (Packagist), Symfony UX or Symfony UX Live Component at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • symfony/ux-live-component (Packagist): upgrade to 2.36.0 or later
    composer require symfony/ux-live-component:^2.36.0

Technical details

A vulnerability exists in Symfony\UX\LiveComponent\LiveComponentHydrator where the HMAC checksum computed for data integrity only covers sorted property key/value pairs. It fails to include the component name, slot identifier (e.g., 'props' vs 'propsFromParent'), or request context in the signature. An attacker can exploit this by taking a valid signed blob from one component or slot and replaying it in another, potentially allowing them to set or overwrite read-only properties on a target component. The issue is addressed by binding the HMAC checksum to the component name and slot in versions 2.36.0 and 3.1.0.

Affected products

  • symfony ux >= 2.8.0, < 2.36.0
  • symfony ux >= 3.0.0, < 3.1.0

Identifiers

  • CVE-2026-49212
  • GHSA-34w5-c283-j9fg

Timeline

  • 2026-05-24: patched: Fix committed to repository
  • 2026-05-29: advisory: Release v2.36.0 and v3.1.0 published
  • 2026-07-17: disclosed: CVE published to NVD

References

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