Squid Proxy Cache Security Update Advisory SQUID-2020:7

 Advisory ID:       | SQUID-2020:7
 Date:              | June 26, 2020
 Summary:           | Cache Poisoning Issue
                    | in HTTP Request processing.
 Affected versions: | Squid 2.x -> 2.7.STABLE9
                    | Squid 3.x -> 3.5.28
                    | Squid 4.x -> 4.11
                    | Squid 5.x -> 5.0.2
 Fixed in version:  | Squid 4.12 and 5.0.3


Problem Description:

 Due to incorrect input validation Squid is vulnerable to a
 Request Smuggling and Poisoning attack against the HTTP cache.



 This problem allows a trusted client to perform request smuggling
 and poison the HTTP cache contents with crafted HTTP(S) request

 This attack requires an upstream server to participate in the
 smuggling and generate the poison response sequence. Most popular
 server software are not vulnerable to participation in this

CVSS Score of 9.3


Updated Packages:

This bug is fixed by Squid versions 4.12 and 5.0.3.

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

Squid 4:

Squid 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-3.x up to and including 3.5.28 are vulnerable.

 All Squid-4.x up to and including 4.11 are vulnerable.

 Squid-5.0.1 and 5.0.2 are vulnerable.



 There is no workaround for this vulnerability.


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...@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-b...@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 Alex Rousskov of The
 Measurement Factory.

 Independent discovery and replication reported by Amit Klein of

 Fixed by Alex Rousskov of The Measurement Factory.


Revision history:

 2016-09-06 02:45:20 UTC Initial Report
 2020-05-11 12:41:17 UTC Replication Reported
 2020-05-13 14:05:00 UTC Patch Released
 2020-06-25 11:15:10 UTC CVE Allocated
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