CVE-2026-49209 in symfony
Summary
by MITRE • 07/17/2026
Symfony UX is a JavaScript ecosystem for Symfony. From 2.5.0 until 2.36.0 and 3.1.0, Symfony\UX\LiveComponent\Controller\BatchActionController::__invoke() iterates over the client-supplied actions array and issues a full HttpKernel sub-request for each entry; because the array size is never bounded, an authenticated client can submit a single _batch request containing thousands of actions and exhaust CPU, memory, and database connections on the application server. 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 exists within Symfony UX LiveComponent's BatchActionController component which processes batch operations submitted by authenticated clients. This flaw resides in the __invoke method of the BatchActionController class where the system iterates over a client-provided actions array without implementing any size limitations or bounds checking. The affected versions span from 2.5.0 through 2.35.0 and all 3.x releases prior to 3.1.0, representing a significant portion of the Symfony UX ecosystem that developers rely upon for building interactive web applications.
The technical implementation flaw stems from the lack of input validation and resource limitation mechanisms within the batch processing logic. When an authenticated user submits a _batch request containing multiple actions, the system creates individual HttpKernel sub-requests for each entry in the actions array. This design pattern becomes problematic when the array contains thousands of entries since each sub-request consumes computational resources including CPU cycles, memory allocation, and database connection pooling. The absence of any upper bound or size restriction on the client-supplied array creates an avenue for resource exhaustion attacks that can severely impact application performance and availability.
This vulnerability represents a classic denial-of-service scenario where legitimate authenticated users can exploit the system's lack of input validation to consume excessive server resources. The operational impact extends beyond simple performance degradation to potentially causing complete service unavailability through resource exhaustion. Each sub-request contributes to CPU utilization, memory consumption, and database connection usage, creating cascading effects that can overwhelm the application server's capacity to handle legitimate requests. The attack vector is particularly concerning because it requires only authentication to execute, making it accessible to any user with valid credentials.
The fix implemented in versions 2.36.0 and 3.1.0 addresses this vulnerability by introducing proper bounds checking and resource limitations on the actions array size. This remediation aligns with security best practices outlined in CWE-400 which categorizes excessive resource consumption as a critical weakness in software systems. The solution follows ATT&CK framework technique T1499.004 for resource exhaustion attacks, where adversaries leverage legitimate system functionality to consume computational resources. Organizations should prioritize upgrading their Symfony UX installations to versions 2.36.0 or 3.1.0 to mitigate this risk. Additionally, implementing rate limiting and request size monitoring at the application level can provide additional defense-in-depth measures against similar vulnerabilities in other components of the Symfony ecosystem.