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      Squid Proxy Cache Security Update Advisory SQUID-2011:1
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Advisory ID:            SQUID-2011:1
Date:                   August 27, 2011
Summary:                Bypass of browser same-origin access
                        control in intercepted communication
Affected versions:      Squid 1.x -> 3.1
                        Squid 3.2 -> 3.2.0.10
Fixed in version:       Squid 3.2.0.11
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     http://www.squid-cache.org/Advisories/SQUID-2011_1.txt
     http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2009-0801
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Problem Description:

 Due to Squid not reusing the original destination address on
 intercepted requests it's possible (even trivial) for flash or
 java applets to bypass the same-origin policy in the browser
 when Squid intercepts HTTP requests.

 The cause to this is that such applets are allowed to perform
 their own HTTP stack, in which case the same-origin policy of
 the browser sandbox only verifies that the applet tries to
 contact the same IP as from where it was loaded at the IP level.
 Squid then uses the Host header to determine which server to
 forward the request to which may be different from the
 connected IP.

 Applies to all Squid releases up to and including 3.2.0.10.

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Severity:

 This problem allows any browser script to bypass local security
 and retrieve arbitrary content from any source.

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Updated Packages:

 This bug is fixed by Squid versions 3.2.0.11

 Due to the design of request handling processes in older Squid
 patches and fixed releases for older versions of Squid are not
 being provided at this time.

 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:

 Squid and its cache are not harmed by this vulnerability. The
 issue is limited to client browsers.

 All Squid releases of any series up to 3.2.0.10 using the
 http_port 'transparent', 'intercept' or 'tproxy' flags are
 active vectors for this browser vulnerability.

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Workarounds:

 Turn off NAT and TPROXY interception. Including the http_port
 'transparent', 'intercept' or 'tproxy' flags in squid.conf.

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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@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@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:

 Thanks to Netspace Ltd and Treehouse Networks Ltd for sponsoring
 the architectural changes in Squid-3.2 leading to this solution.

 Thanks to Henrik Nordstrom and Steven Wilton for initial diagnosis.

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Revision history:

 2011-08-27 10:06 GMT Initial version
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