[squid-announce] [ADVISORY] SQUID-2023:10 Denial of Service in HTTP Request parsing

[Amos Jeffries]

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   Squid Proxy Cache Security Update Advisory SQUID-2023:10
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Advisory ID:       | SQUID-2023:10
Date:              | Dec 10, 2023
Summary:           | Denial of Service in HTTP Request parsing
Affected versions: | Squid 2.6 -> 2.7.STABLE9
                    | Squid 3.1 -> 3.5.28
                    | Squid 4.x -> 4.17
                    | Squid 5.x -> 5.9
                    | Squid 6.x -> 6.5
Fixed in version:  | Squid 6.6
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Problem Description:

  Due to an Uncontrolled Recursion bug, Squid may be vulnerable to a
  Denial of Service attack against HTTP Request parsing.

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Severity:

This problem allows a remote client to perform Denial of Service attack
by sending a large X-Forwarded-For header when the
follow_x_forwarded_for feature is configured.

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Updated Packages:

     This bug is fixed by Squid version 6.6.

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

Squid 5:
  <http://www.squid-cache.org/Versions/v5/SQUID-2023_10.patch>

Squid 6:
  <http://www.squid-cache.org/Versions/v6/SQUID-2023_10.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:

  To check for follow_x_forwarded_for run the following command:

   `squid -k parse 2>&1 |grep follow_x_forwarded_for`


  All Squid configured without follow_x_forwarded_for are not
  vulnerable.

  All Squid older than 5.0.5 have not been tested and should be
  assumed to be vulnerable when configured with
  follow_x_forwarded_for.

  All Squid-5.x up to and including 5.9 are vulnerable when
  configured with follow_x_forwarded_for.

  All Squid-6.x up to and including 6.5 are vulnerable when
  configured with follow_x_forwarded_for.

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Workaround:

  Remove all follow_x_forwarded_for lines from 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 you 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
  <https://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 Joshua Rogers of Opera
  Software.

  Fixed by Thomas Leroy of the SUSE security team.

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Revision history:

  2023-10-12 11:53:02 UTC Initial Report
  2023-11-28 07:35:46 UTC Patches Released
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