Navigation Bar Top Applications Support Documentation Vendors Search Index Top Top

varnish -- DoS vulnerability in Varnish HTTP cache


Varnish Cache Project reports:

If Varnish receives a certain illegal request, and the subroutine 'vcl_error{}' restarts the request, the varnishd worker process will crash with an assert.

The varnishd management process will restart the worker process, but there will be a brief interruption of service and the cache will be emptied, causing more traffic to go to the backend.

We are releasing this advisory because restarting from vcl_error{} is both fairly common and documented.

This is purely a denial of service vulnerability, there is no risk of privilege escalation.


Insert this at the top of your VCL file:

		sub vcl_error {
			if (obj.status == 400 || obj.status == 413) {

		Or add this test at the top of your existing vcl_error{}.



portaudit: varnish -- DoS vulnerability in Varnish HTTP cache

Disclaimer: The data contained on this page is derived from the VuXML document, please refer to the the original document for copyright information. The author of portaudit makes no claim of authorship or ownership of any of the information contained herein.

If you have found a vulnerability in a FreeBSD port not listed in the database, please contact the FreeBSD Security Team. Refer to "FreeBSD Security Information" for more information.

Oliver Eikemeier <>