[squid-announce] SQUID-2021:8 Denial of Service in Gopher gateway

[Amos Jeffries]

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   Squid Proxy Cache Security Update Advisory SQUID-2021:8
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Advisory ID:       | SQUID-2021:8
Date:              | September 27, 2023
Summary:           | Denial of Service in Gopher gateway
Affected versions: | Squid 2.x -> 2.7.STABLE9
                    | Squid 3.x -> 3.5.28
                    | Squid 4.x -> 4.16
                    | Squid 5.x -> 5.9
Fixed in version:  | Squid 6.0.1
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Problem Description:

  Due to a NULL pointer de-reference bug Squid is vulnerable to
  a Denial of Service attack against Squid's Gopher gateway.

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Severity:

  The gopher protocol is always available and enabled in Squid
  prior to Squid 6.0.1

  Responses triggering this bug are possible to be received from
  any gopher server, even those without malicious intent.

  CVSS Score of 7.5
<https://nvd.nist.gov/vuln-metrics/cvss/v3-calculator?vector=AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H&version=3.1>

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Updated Packages:

    The gopher support has been removed in 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:

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

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

  All Squid-4.x up to and including 4.16 are vulnerable.

  All Squid-5.x up to and including 5.9 are vulnerable.

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Workaround:

* Reject all gopher URL requests

   acl gopher proto gopher
   http_access deny gopher

  Note: removing the gopher port 70 from the Safe_ports ACL
        is not sufficient to avoid this vulnerability.
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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.

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Revision history:

  2021-02-20 08:37:38 UTC Initial Report
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