[squid-announce] [ADVISORY] SQUID-2019:9 Cross-Site Request Forgery issue in HTTP Request processing

[Amos Jeffries]

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    Squid Proxy Cache Security Update Advisory SQUID-2019:9
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Advisory ID:        SQUID-2019:9
Date:               November 05, 2019
Summary:            Cross-Site Request Forgery issue
                    in HTTP Request processing.
Affected versions:  Squid 2.x -> 2.7.STABLE9
                    Squid 3.x -> 3.5.28
                    Squid 4.x -> 4.8
Fixed in version:   Squid 4.9
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    http://www.squid-cache.org/Advisories/SQUID-2019_9.txt
    http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-18677
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Problem Description:

 Due to incorrect message processing Squid configured with
 append_domain can inappropriately redirect traffic to origins it
 should not be delivered to.

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Severity:

 This issue allows attackers to hide origin servers for phishing
 attacks or malware download URLs.

 This issue is restricted to proxies with append_domain
 configured. It is relatively easy for attackers to probe and
 determine whether a target network proxy has this directive
 along with its value.

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Updated Packages:

 This bug is fixed by Squid version 4.9.

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

Squid 3.5:
 <http://www.squid-cache.org/Versions/v3/3.5/changesets/squid-3.5-e5f1813a674848dde570f7920873e1071f96e0b4.patch>

Squid 4:
 <http://www.squid-cache.org/Versions/v4/changesets/squid-4-36492033ea4097821a4f7ff3ddcb971fbd1e8ba0.patch>

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

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Determining if your version is vulnerable:

 All Squid without append_domain configured are not vulnerable.

 All Squid-2.x up to and including 2.7.STABLE9 with append_domain
 configured are vulnerable.

 All Squid-3.x up to and including 3.5.28 with append_domain
 configured are vulnerable.

 All Squid-4.x up to and including 4.8 with append_domain
 configured are vulnerable.


To determine whether append_domain is configured use the command:

 squid -k parse | grep append_domain

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Workarounds:

 Remove append_domain configuration settings from squid.conf.

 The append_domain feature is redundant when /etc/resolv.conf
 is used to determine hostnames. However, please note that use
 of /etc/resolv.conf may require removal of dns_nameservers and
 other redundant DNS directives.

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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 at lists.squid-cache.org mailing list is your
 primary support point. For subscription details see
 <http://www.squid-cache.org/Support/mailing-lists.html>.

 For reporting of non-security bugs in the latest STABLE release
 the squid bugzilla database should be used
 <http://bugs.squid-cache.org/>.

 For reporting of security sensitive bugs send an email to the
 squid-bugs at 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.

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Credits:

 This vulnerability was discovered by Kristoffer Danielsson.

 Fixed by Amos Jeffries of Treehouse Networks Ltd.

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Revision history:

 2019-06-26 21:43:49 UTC Initial Report
 2019-07-12 03:08:00 UTC Patches Released
 2019-11-04 13:43:22 UTC CVE-2019-18677 Assignment
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END