An HTTP method is safe when used to perform a read-only operation, such as retrieving information. In contrast, an unsafe HTTP method is used to change the state of an application, for instance to update a user's profile on a web application.

Common safe HTTP methods are GET, HEAD, or OPTIONS.

Common unsafe HTTP methods are POST, PUT and DELETE.

Allowing both safe and unsafe HTTP methods to perform a specific operation on a web application could impact its security, for example CSRF protections are most of the time only protecting operations performed by unsafe HTTP methods.

Ask Yourself Whether

There is a risk if you answered yes to any of those questions.

Recommended Secure Coding Practices

For all the routes/controllers of an application, the authorized HTTP methods should be explicitly defined and safe HTTP methods should only be used to perform read-only operations.

Sensitive Code Example

@RequestMapping("/delete_user")  // Sensitive: by default all HTTP methods are allowed
public String delete1(String username) {
// state of the application will be changed here
}

@RequestMapping(path = "/delete_user", method = {RequestMethod.GET, RequestMethod.POST}) // Sensitive: both safe and unsafe methods are allowed
String delete2(@RequestParam("id") String id) {
// state of the application will be changed here
}

Compliant Solution

@RequestMapping("/delete_user", method = RequestMethod.POST)  // Compliant
public String delete1(String username) {
// state of the application will be changed here
}

@RequestMapping(path = "/delete_user", method = RequestMethod.POST) // Compliant
String delete2(@RequestParam("id") String id) {
// state of the application will be changed here
}

See