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                                 CERT-Renater

                     Note d'Information No. 2016/VULN063
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DATE                : 19/02/2016

HARDWARE PLATFORM(S): /

OPERATING SYSTEM(S): Systems running Squid.

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http://www.squid-cache.org/Advisories/SQUID-2016_1.txt
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Squid Proxy Cache Security Update Advisory SQUID-2016:1
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Advisory ID:        SQUID-2016:1
Date:               February 16, 2016
Summary:            Remote Denial of service issue
                     in SSL/TLS processing.
Affected versions:  Squid 3.5.13
                     Squid 4.0.4 -> 4.0.5
Fixed in version:   Squid 4.0.6, 3.5.14
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     http://www.squid-cache.org/Advisories/SQUID-2016_1.txt
     http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-2390
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Problem Description:

  Due to incorrectly handling server errors Squid is vulnerable to
  a denial of service attack when connecting to TLS or SSL servers.

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Severity:

  This problem allows any trusted client to perform a denial of
  service attack on the Squid service regardless of whether TLS or
  SSL is configured for use in the proxy.

  Misconfigured client or server software may trigger this issue
  to perform a denial of service unintentionally.

  However, the bug is exploitable only if Squid is built using the
  --with-openssl option.

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Updated Packages:

  These bugs are fixed by Squid version 3.5.14 and 4.0.6.


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

Squid 3.5:
 
http://www.squid-cache.org/Versions/v3/3.5/changesets/squid-3.5-13981.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-3.4 and older versions are not vulnerable.

  All Squid-3.5.12 and older 3.5 versions are not vulnerable.

  All Squid-3.5 built without OpenSSL support are not vulnerable.

  All Squid-4.0.3 and older 4.0 versions are not vulnerable.

  All Squid-4 built without OpenSSL support are not vulnerable.

  All unpatched Squid-3.5.13, 4.0.4, and 4.0.5 built using
  --with-openssl are vulnerable.

  The following command can be used to easily determine if a
  vulnerable build is being used:
   squid -v

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Workaround:

  Disabling service for https:// URLs entirely at the top of the
  squid.conf http_access rules fully protects against this
  vulnerability:

    acl HTTPS proto HTTPS
    http_access deny HTTPS

Or,

  Relaying outbound HTTPS traffic through a non-vulnerable proxy
  protects against the issue unless the SSL-bump splice feature is
  being used.

Or,

  Disabling service for irregular HTTPS ports protects against the
  simplest forms of attack while retaining most HTTPS service:

    acl HTTPS proto HTTPS
    http_access deny HTTPS !SSL_Ports

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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@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@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:

  The vulnerability was reported by Mathias Fischer and Fabian
  Hugelshofer from Open Systems AG.

  The vulnerability was fixed by Christos Tsantilas of The
  Measurement Factory.

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Revision history:

  2016-02-12 17:50:38 GMT Initial Report
  2016-02-12 18:05:44 GMT Patch Released
  2016-02-15 17:15:00 GMT Packages Released
  2016-02-16 14:45:01 GMT CVE Assignment
  2016-02-16 23:33:52 GMT Updated reporter credits
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END

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