Vigil@nce - Apache httpd: denial of service via HTTP version 2
July 2016 by Vigil@nce
This bulletin was written by Vigil@nce : https://vigilance.fr/offer
SYNTHESIS OF THE VULNERABILITY
An attacker can send HTTP 2 requests over a TCP connection with
unusual flow control window to Apache httpd, in order to trigger a
denial of service.
Impacted products: Apache httpd.
Severity: 1/4.
Creation date: 07/07/2016.
DESCRIPTION OF THE VULNERABILITY
The Apache httpd product implements HTTP version 2.
The protocol HTTP version 2 allows to multiplex several requests
and related responses over one TCP connection (while HTTP 1 only
allows a sequence of pairs (full request, full response)).
However, when the client announces non standard TCP flow control
window, httpd allocates too many control thread to this
connection, which prevents it to serve other clients.
An attacker can therefore send HTTP 2 requests over a TCP
connection with unusual flow control window to Apache httpd, in
order to trigger a denial of service.
ACCESS TO THE COMPLETE VIGIL@NCE BULLETIN
https://vigilance.fr/vulnerability/Apache-httpd-denial-of-service-via-HTTP-version-2-20039