Uncontrolled Resource Consumption
symfony/symfony and symfony/http-foundation before 2.3.19, 2.4.x before 2.4.9, and 2.5.x before 2.5.4 are vulnerable to regex denial of service (ReDoS). When an arbitrarily long hostname is sent by a client, its parsing in Request::getHost() can lead to a DoS attack, due to the way the hostname is validated via a regular expression.
CWE-400 - Uncontrolled resource consumption
An uncontrolled resource allocation attack (also known as resource exhaustion attack) triggers unauthorized overconsumption of the limited resources in an application, such as memory, file system storage, database connection pool entries, and CPU. This may lead to denial of service for valid users and degradation of the application's functionality as well as that of the host operating system.