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             AUSCERT External Security Bulletin Redistribution

                Squid Proxy Cache Security Update Advisory
                              29 October 2018


        AusCERT Security Bulletin Summary

Product:           Squid
Publisher:         Squid
Operating System:  UNIX variants (UNIX, Linux, OSX)
                   BSD variants
Impact/Access:     Cross-site Scripting -- Remote with User Interaction
Resolution:        Patch/Upgrade

Original Bulletin: 

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    Squid Proxy Cache Security Update Advisory SQUID-2018:4

Advisory ID:        SQUID-2018:4
Date:               October 28, 2018
Summary:            Cross-Site Scripting issue
                    in TLS error processing.
Affected versions:  Squid -> 3.1.23
                    Squid -> 3.5.28
                    Squid 4.0 -> 4.3
Fixed in version:   Squid 4.4


Problem Description:

 Due to incorrect input handling, Squid is vulnerable to a
 Cross-Site Scripting vulnerability when generating HTTPS response
 messages about TLS errors.



 This problem allows a malicious HTTPS server to trigger error
 page delivery to a client and also inject arbitrary HTML code
 into the resulting error response.

 This problem is limited to Squid built with TLS / SSL support.


Updated Packages:

 This bug is fixed by Squid version 4.4.

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

Squid 3.5:

Squid 4:

 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-2.x and older are not vulnerable.

 All Squid-3.0 and older version are not vulnerable.

 All Squid-3.x versions up to and including 3.4.14 built with
 --disable-ssl are not vulnerable.

 All Squid-3.x versions up to and including 3.4.14 built without
 --enable-ssl are not vulnerable.

 All Squid- and later versions up to and including
 Squid-3.1.23 built with --enable-ssl are vulnerable.

 All Squid- and later versions up to and including
 Squid-3.2.14 built with --enable-ssl are vulnerable.

 All Squid-3.3 and later versions up to and including
 Squid-3.3.14 built with --enable-ssl are vulnerable.

 All Squid-3.4 and later versions up to and including
 Squid-3.4.14 built with --enable-ssl are vulnerable.

 All Squid-3.5 versions up to and including 3.5.28 built without
 --with-openssl are not vulnerable.

 All Squid-3.5 and later versions up to and including 3.5.28 built
 with --with-openssl are vulnerable.

 All Squid-4 versions built without --with-openssl are not

 All Squid-4 versions up to and including 4.3 built with
 --with-openssl are vulnerable.




 Remove %D error page macro from ERR_SECURE_CONNECT_FAIL and any
 custom error pages.


 Build Squid-3.1 to 3.4.14 without "--enable-ssl"


 Build Squid-3.5 or later without "--with-openssl"


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 your 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 STABLE 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.



 This vulnerability was discovered by Nikolas Lohmann of eBlocker

 Fixed by Christos Tsantilas on behalf of Measurement Factory.


Revision history:

 2018-10-15 10:59:16 UTC Initial Report
 2018-10-17 15:13:41 UTC Patches Released
 2018-10-27 21:19:00 UTC Packages Released

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