[squid-announce] [ADVISORY] SQUID-2023:9 Denial of Service in HTTP Collapsed Forwarding

[Amos Jeffries]

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    Squid Proxy Cache Security Update Advisory SQUID-2023:9
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Advisory ID:       | SQUID-2023:9
Date:              | December 1, 2023
Summary:           | Denial of Service
                    | in HTTP Collapsed Forwarding
Affected versions: | Squid 3.5 -> 3.5.28
                    | Squid 4.x -> 4.17
                    | Squid 5.x -> 5.9
Fixed in version:  | Squid 6.0.1
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Problem Description:

  Due to a Use-After-Free bug Squid is vulnerable to a Denial of
  Service attack against collapsed forwarding

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Severity:

  This problem allows a remote client to perform Denial of
  Service attack on demand when Squid is configured with collapsed
  forwarding.

CVSS Score of 8.6
<https://nvd.nist.gov/vuln-metrics/cvss/v3-calculator?vector=AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H&version=3.1>

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Updated Packages:

This bug is fixed by Squid version 6.0.1.

  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:

  Run the following command to identify how (and whether)
  your Squid has been configured with collapsed forwarding:

     squid -k parse 2>&1 | grep collapsed_forwarding


  All Squid-3.5 up to and including 5.9 configured with
  "collapsed_forwarding on" are vulnerable.

  All Squid-3.5 up to and including 5.9 configured with
  "collapsed_forwarding off" are not vulnerable.

  All Squid-3.5 up to and including 5.9 configured without any
  "collapsed_forwarding" directive are not vulnerable.

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Workaround:

  Remove all collapsed_forwarding lines from your 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 The Measurement Factory.

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Revision history:

  2022-09-03 18:41:32 UTC Patches Released
  2023-10-12 11:53:02 UTC Initial Report
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