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             AUSCERT External Security Bulletin Redistribution

          Squid Proxy Cache Security Update Advisory SQUID-2015:2
                   Improper Protection of Alternate Path
                               6 August 2015


        AusCERT Security Bulletin Summary

Product:           Squid
Publisher:         Squid
Operating System:  Windows
                   UNIX variants (UNIX, Linux, OSX)
Impact/Access:     Unauthorised Access -- Remote/Unauthenticated
Resolution:        Patch/Upgrade

Original Bulletin: 

Revision History:  August 6 2015: Patch for 3.1 added
                   July   9 2015: Initial Release

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    Squid Proxy Cache Security Update Advisory SQUID-2015:2

Advisory ID:            SQUID-2015:2
Date:                   July 06, 2015
Summary:                Improper Protection of Alternate Path
Affected versions:      Squid 0.x -> 3.5.5
Fixed in version:       Squid 3.5.6


Problem Description:

 Squid configured with cache_peer and operating on explicit proxy
 traffic does not correctly handle CONNECT method peer responses.



 The bug is important because it allows remote clients to bypass
 security in an explicit gateway proxy.

 However, the bug is exploitable only if you have configured
 cache_peer to receive CONNECT requests.


Updated Packages:

 This bug is fixed by Squid version 3.5.6.

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

Squid 3.1:

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 Squid versions with cache_peer omitted from squid.conf are
 not vulnerable to the problem.

 All Squid versions with squid.conf containing
 "nonhierarchical_direct on" are not vulnerable to the problem.

 All Squid-3.1 and later with nonhierarchical_direct omitted from
 squid.conf are not vulnerable to the problem.

 All other unpatched Squid configured to use a cache_peer without
 the "originserver" option are vulnerable to the problem.



 For Squid-3.0 and older ensure squid.conf contains
 "nonhierarchical_direct on".

 For Squid-3.1 and newer remove nonhierarchical_direct from


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-users@lists.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-bugs@lists.squid-cache.org mailing list. It's 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 and fixed by Alex Rousskov, The
 Measurement Factory.

 Squid-3.1 backport by Raphaël Hertzog, Debian Project.


Revision history:

 2015-06-16 16:54 GMT Initial Report and Patches Released
 2015-05-03 15:37 GMT Packages Released
 2015-07-17 14:09 GMT CVE Assigment
 2015-07-30 15:57 GMT Patch for 3.1 added

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