symfony/ux-live-component: LiveComponentHydrator HMAC checksum lacks component and slot binding

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

2.3 · CVSS:4.0/AV:N/AC:H/AT:N/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2026-49212: 0.24% estimated exploitation activity in the next 30 days; percentile 15.39 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Description In symfony/ux-live-component, a component's server-side state is exposed to the browser as a set of props (#[LiveProp]-annotated properties). Props marked writable: true can be freely changed by the client. Read-only props are round-tripped to the browser and back, and their integrity is protected by an HMAC so the client cannot tamper with them. Child components additionally receive a propsFromParent blob, also HMAC-signed. The HMAC computed by Symfony\UX\LiveComponent\LiveComponentHydrator covered only the sorted prop key/value pairs. It didn't include the component name, the slot identifier (props vs propsFromParent), or any request context, and a single application-wide secret is used for every component. A signed blob the server minted for component A is therefore a valid signature for component B if the key names happen to match, and a props blob can be replayed in the propsFromParent slot (or the reverse). An attacker can use this to set a read-only prop on a…

Published by the source

19 Jun 2026, 19:34 UTC

Last modified by the source

19 Jun 2026, 19:34 UTC

Source last checked

26 Oct 2026, 14:49 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-34w5-c283-j9fg

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# Patch Next advisory brief: CVE-2026-49212

Advisory: symfony/ux-live-component: LiveComponentHydrator HMAC checksum lacks component and slot binding
IDs: CVE-2026-49212, GHSA-34w5-c283-j9fg
Record: https://patchnext.com/advisories/cve-2026-49212 (revision 1, source checked 26 Oct 2026, 14:49 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 2.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: symfony/ux-live-component 3.1.0, 2.36.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist symfony/ux-live-component: affected >= 2.8.0, < 2.36.0; >= 3.0.0, < 3.1.0; fixed in 3.1.0, 2.36.0

## Suggested inspection (read-only)
- Packagist symfony/ux-live-component: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on symfony/ux-live-component.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-34w5-c283-j9fg (GitHub-reviewed advisory GHSA-34w5-c283-j9fg lists affected ranges: Packagist symfony/ux-live-component >=2.8.0 =3.0.0 <3.1.0)

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