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CVE-2026-49212 high CVSS 7.5

Vulnerability in symfony/ux-live-component (CVE-2026-49212)

Summary

Vulnerability in symfony/ux-live-component (CVE-2026-49212). Data can be tampered with by attackers. Exploitable via propsFromParent. Mitigation: upgrade to 3.1.0 or later.

Original description

The description as published by the source.

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 target component to a value they were only ever allowed to choose as a writable prop on another component.

Resolution

The HMAC is now bound to its context: the component name and a slot identifier are included in the pre-image before hashing. Two constants (CHECKSUM_SLOT_PROPS and CHECKSUM_SLOT_PROPS_FROM_PARENT) name the two slots, and calculateChecksum(), verifyChecksum(), addChecksumToData(), and ChildComponentPartialRenderer thread these values through. Cro…

Source: GitHub Security Advisories (Global) NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-49212 has been found in symfony/ux-live-component.
Attackers can target a specific entry point like propsFromParent over the network to misuse the product.
Data can be tampered with by attackers. CVSS score: 7.5/10.
What to do: upgrade symfony/ux-live-component to 3.1.0 or later.
If unsure, ask your IT team or search "symfony/ux-live-component CVE-2026-49212" on the vendor's site.

CVE-2026-49212 (symfony/ux-live-component) — CWE-345 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: propsFromParent / props / CHECKSUM_SLOT_PROPS / CHECKSUM_SLOT_PROPS_FROM_PARENT
Patched: 3.1.0 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

A vulnerability (CWE-345) exists in symfony/ux-live-component. Attackers reach the vulnerable code path via propsFromParent without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of symfony/ux-live-component. Attack surface: propsFromParent / props / CHECKSUM_SLOT_PROPS / CHECKSUM_SLOT_PROPS_FROM_PARENT.

🔥 Severity

Severity: High (CVSS 7.5/10). Data can be tampered with by attackers.

🔧 How to fix

Update to 3.1.0.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'symfony/ux-live-component' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    grep -r 'symfony/ux-live-component' . | grep -v node_modules

    リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で symfony/ux-live-component を grep し、稼働しているサービス・バージョンを把握する。

  2. 2
    Apply patch patch 
    Upgrade symfony/ux-live-component to 3.1.0

    ステージング環境で 3.1.0 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。

  3. 3
    Post-deployment verification verify 
    Confirm patched version is live in production

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

composer symfony/ux-live-component
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.1.0"}]}]
Packagist symfony/ux-live-component
[{"type":"ECOSYSTEM","events":[{"introduced":"3.0.0"},{"fixed":"3.1.0"}]}]

References

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