CVE-2026-49215 in Symfony
Summary
by MITRE • 07/17/2026
Symfony UX is a JavaScript ecosystem for Symfony. From 2.22.0 until 2.36.0 and 3.1.0, Symfony\UX\LiveComponent\EventListener\LiveComponentSubscriber::isLiveComponentRequest() gates #[LiveAction] invocations on Accept: application/vnd.live-component+html, but the Accept header is CORS-safelisted and cross-origin fetch() can set it without preflight, allowing forged cross-origin #[LiveAction] requests against a victim session when applications use SameSite=None, credentials: 'include', a permissive cookie policy, or a same-origin pivot. This issue is fixed in versions 2.36.0 and 3.1.0.
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Analysis
by VulDB Data Team • 07/17/2026
The vulnerability affects Symfony UX LiveComponent functionality across versions 2.22.0 through 2.36.0 and 3.1.0, representing a critical security flaw in the JavaScript ecosystem for Symfony applications. This issue stems from improper validation of HTTP request origins within the LiveComponentSubscriber class, specifically in the isLiveComponentRequest() method that relies on the Accept header for authorization. The vulnerability creates a cross-site request forgery (CSRF) attack vector by exploiting the CORS safelisting mechanism of the Accept header.
The technical flaw manifests when applications use session-based authentication with SameSite=None cookies and credentials: 'include' settings, or employ permissive cookie policies that allow cross-origin requests to include session data. The Accept header is inherently safelisted in CORS specifications, meaning browsers permit cross-origin fetch() operations to set this header without requiring a preflight OPTIONS request. This behavior allows malicious actors to forge requests that appear to originate from legitimate sources within the target application's domain.
When applications configure their cookie policies with SameSite=None and include credentials in cross-origin requests, attackers can construct malicious requests that leverage the LiveComponent subsystem to execute unauthorized #[LiveAction] operations against victim sessions. The vulnerability becomes particularly dangerous when combined with a same-origin pivot attack where an attacker first establishes a foothold on a legitimate domain before using the forged Accept header to target other domains within the same application ecosystem. This exploitation pattern aligns with attack techniques documented in the ATT&CK framework under web application attacks and session management vulnerabilities.
The operational impact of this vulnerability extends beyond simple CSRF attacks, as it can enable unauthorized modifications to live components, data manipulation, or even privilege escalation depending on the application's configuration. Attackers could potentially execute arbitrary actions against user sessions without proper authorization, especially in applications that rely heavily on server-side rendered components and dynamic UI updates. The vulnerability affects any Symfony application utilizing LiveComponent functionality where session management is configured with permissive cross-origin policies.
Mitigation strategies should focus on implementing additional authentication checks beyond the Accept header validation, such as requiring custom headers or tokens for LiveAction execution. Applications should avoid using SameSite=None cookies unless absolutely necessary, and implement proper CORS policies that restrict which origins can access live component endpoints. The fix implemented in versions 2.36.0 and 3.1.0 addresses this by strengthening the request validation mechanism to ensure that LiveComponent actions cannot be forged through cross-origin requests without proper authentication tokens or additional security headers. Organizations should also consider implementing Content Security Policy directives that restrict which origins can perform live component operations, as recommended in CWE-352 standards for CSRF protection.