Arch Linux Security Advisory ASA-202107-28
=========================================
Severity: Medium
Date    : 2021-07-14
CVE-ID  : CVE-2021-36740
Package : varnish
Type    : url request injection
Remote  : Yes
Link    : https://security.archlinux.org/AVG-2154

Summary
======
The package varnish before version 6.6.1-1 is vulnerable to url request
injection.

Resolution
=========
Upgrade to 6.6.1-1.

# pacman -Syu "varnish>=6.6.1-1"

The problem has been fixed upstream in version 6.6.1.

Workaround
=========
The issue can be mitigated by turning off support for HTTP/2, using

sudo varnishadm param.set feature -http2

or by preventing connection reuse with the following configuration:

sub vcl_backend_fetch {
      set bereq.http.Connection = "close";
}

Description
==========
Varnish Cache before version 6.6.1, with HTTP/2 enabled, allows request
smuggling and VCL authorization bypass via a large Content-Length
header for a POST request.

Impact
=====
A remote attacker could inject arbitrary HTTP requests through an
HTTP/2 POST request with a large Content-Length header.

References
=========
https://varnish-cache.org/security/VSV00007.html
https://github.com/varnishcache/varnish-cache/commit/7d73bc843ea9bff79e33773f1cfe2dffa7d03ea1
https://security.archlinux.org/CVE-2021-36740