Squid Proxy Cache Security Update Advisory SQUID-2016:8

Advisory ID:        SQUID-2016:8
Date:               May 06, 2016
Summary:            Header smuggling issue
                    in HTTP Request processing
Affected versions:  Squid 1.x -> 3.5.17
Fixed in version:   Squid 3.5.18


Problem Description:

 Due to incorrect input validation Squid is vulnerable to a header
 smuggling attack leading to cache poisoning and to bypass of
 same-origin security policy in Squid and some client browsers.



 This problem allows a client to smuggle Host header value past
 same-origin security protections to cause Squid operating as
 interception or reverse-proxy to contact the wrong origin
 server. Also poisoning any downstream cache which stores the

 However, the cache poisoning is only possible if the caching
 agent (browser or explicit/forward proxy) is not following RFC
 7230 processing guidelines and lets the smuggled value through.


Updated Packages:

 This bug is fixed by Squid version 3.5.18

 In addition, patches addressing this problem for stable releases
 can be found in our patch archives:

Squid 3.1:

Squid 3.2:

Squid 3.3:

Squid 3.4:

Squid 3.5:

 If you are using a prepackaged version of Squid then please refer
 to the package vendor for availability information on updated


Determining if your version is vulnerable:

  All 2.x versions up to and including 2.7.STABLE9 are vulnerable.

  All 3.x versions up to and including 3.5.17 are vulnerable.

  All 4.x versions are not vulnerable.



 There are no workarounds for this problem.


Contact details for the Squid project:

 For installation / upgrade support on binary packaged versions
 of Squid: Your first point of contact should be your binary
 package vendor.

 If you install and build Squid from the original Squid sources
 then the squid-us...@squid-cache.org mailing list is your
 primary support point. For subscription details see

 For reporting of non-security bugs in the latest release
 the squid bugzilla database should be used

 For reporting of security sensitive bugs send an email to the
 squid-b...@squid-cache.org mailing list. It is a closed list
 (though anyone can post) and security related bug reports are
 treated in confidence until the impact has been established.



 The vulnerability was reported by Jianjun Chen from Tsinghua

 Fixed by Amos Jeffries from Treehouse Networks Ltd.


Revision history:

 2016-04-26 09:29:13 UTC Initial Report
 2016-05-02 03:39:35 UTC Patches Released
 2016-05-06 13:12:00 UTC Packages Released
 2016-05-06 14:46:41 UTC CVE Assignment
 2016-05-08 12:45:58 UTC Patches Updated
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