CVE-2019-16789

In Waitress through version 1.4.0, if a proxy server is used in front of waitress, an invalid request may be sent by an attacker that bypasses the front-end and is parsed differently by waitress leading to a potential for HTTP request smuggling. Specially crafted requests containing special whitespace characters in the Transfer-Encoding header would get parsed by Waitress as being a chunked request, but a front-end server would use the Content-Length instead as the Transfer-Encoding header is considered invalid due to containing invalid characters. If a front-end server does HTTP pipelining to a backend Waitress server this could lead to HTTP request splitting which may lead to potential cache poisoning or unexpected information disclosure. This issue is fixed in Waitress 1.4.1 through more strict HTTP field validation.

In Waitress through version 1.4.0, if a proxy server is used in front of waitress, an invalid request may be sent by an attacker that bypasses the front-end and is parsed differently by waitress leading to a potential for HTTP request smuggling. Specially crafted requests containing special whitespace characters in the Transfer-Encoding header would get parsed by Waitress as being a chunked request, but a front-end server would use the Content-Length instead as the Transfer-Encoding header is considered invalid due to containing invalid characters. If a front-end server does HTTP pipelining to a backend Waitress server this could lead to HTTP request splitting which may lead to potential cache poisoning or unexpected information disclosure. This issue is fixed in Waitress 1.4.1 through more strict HTTP field validation.

In Waitress through version 1.4.0, if a proxy server is used in front of waitress, an invalid request may be sent by an attacker that bypasses the front-end and is parsed differently by waitress leading to a potential for HTTP request smuggling. Specially crafted requests containing special whitespace characters in the Transfer-Encoding header would get parsed by Waitress as being a chunked request, but a front-end server would use the Content-Length instead as the Transfer-Encoding header is considered invalid due to containing invalid characters. If a front-end server does HTTP pipelining to a backend Waitress server this could lead to HTTP request splitting which may lead to potential cache poisoning or unexpected information disclosure. This issue is fixed in Waitress 1.4.1 through more strict HTTP field validation.

### Impact The patches introduced to fix https://github.com/Pylons/waitress/security/advisories/GHSA-m5ff-3wj3-8ph4 were not complete and still would allow an attacker to smuggle requests/split a HTTP request with invalid data. This updates the existing CVE with ID: CVE-2019-16789 ### Patches Waitress version 1.4.2 has been updated to now validate HTTP headers better to avoid the issue, completely fixing all known issues with whitespace. ### Workarounds There are no work-arounds, upgrading to Waitress 1.4.2 is highly recommended. ### References See https://github.com/Pylons/waitress/security/advisories/GHSA-m5ff-3wj3-8ph4 for more information on the security issue. ### For more information If you have any questions or comments about this advisory: * open an issue at https://github.com/Pylons/waitress/issues (if not sensitive or security related) * email the Pylons Security mailing list: pylons-project-security@googlegroups.com (if security related)

En Waitress versiones hasta 1.4.0, si un servidor proxy es usado frente a waitress, un atacante puede enviar una petición no comprobada que omita el front-end y que waitress analiza de manera diferente conllevando a un posible trafico no autorizado de peticiones HTTP. Waitress analizaría las peticiones especialmente diseñadas que contienen caracteres de espacio en blanco especiales en el encabezado Transfer-Encoding como si fuera una petición fragmentada, pero un servidor front-end usaría Content-Length en su lugar ya que el encabezado Transfer-Encoding es considerado no válido debido a que contiene caracteres no válidos. Si un servidor de aplicaciones para usuario establece una canalización HTTP hacia un servidor backend de Waitress, esto podría conllevar a una división de la petición HTTP, lo que podría generar un posible envenenamiento de la caché o una divulgación inesperada de información. Este problema se soluciona en Waitress versión 1.4.1 por medio de una comprobación del campo HTTP más estricta.