symfony ux up to 2.35.x/3.0.x LiveComponentHydrator authentication replay

Summaryinfo

A vulnerability, which was classified as critical, was found in symfony ux up to 2.35.x/3.0.x. Affected by this issue is some unknown functionality of the component LiveComponentHydrator. Executing a manipulation can lead to authentication replay. The identification of this vulnerability is CVE-2026-49212. The attack may be launched remotely. There is no exploit available.

Detailsinfo

A vulnerability classified as critical was found in symfony ux up to 2.35.x/3.0.x. This vulnerability affects some unknown functionality of the component LiveComponentHydrator. The manipulation with an unknown input leads to a authentication replay vulnerability. The CWE definition for the vulnerability is CWE-294. A capture-replay flaw exists when the design of the product makes it possible for a malicious user to sniff network traffic and bypass authentication by replaying it to the server in question to the same effect as the original message (or with minor changes). As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

Symfony UX is a JavaScript ecosystem for Symfony. From 2.8.0 until 2.36.0 and 3.1.0, the HMAC computed by Symfony\UX\LiveComponent\LiveComponentHydrator covered only sorted prop key/value pairs and did not include the component name, the slot identifier (props vs propsFromParent), or request context, allowing a signed blob minted for one component or slot to be replayed in another and set a read-only prop on a target component. This issue is fixed in versions 2.36.0 and 3.1.0.

The advisory is shared for download at github.com. This vulnerability was named CVE-2026-49212 since 05/28/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. There are neither technical details nor an exploit publicly available. The MITRE ATT&CK project declares the attack technique as T1040.

Upgrading to version 2.36.0 or 3.1.0 eliminates this vulnerability.

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Productinfo

Vendor

• symfony

Name

• ux

Version

• 2.0
• 2.1
• 2.2
• 2.3
• 2.4
• 2.5
• 2.6
• 2.7
• 2.8
• 2.9
• 2.10
• 2.11
• 2.12
• 2.13
• 2.14
• 2.15
• 2.16
• 2.17
• 2.18
• 2.19
• 2.20
• 2.21
• 2.22
• 2.23
• 2.24
• 2.25
• 2.26
• 2.27
• 2.28
• 2.29
• 2.30
• 2.31
• 2.32
• 2.33
• 2.34
• 2.35
• 3.0

License

• open-source

Website

• Product: https://github.com/symfony/ux/

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