[squid-announce] [ADVISORY] SQUID-2023:5 Denial of Service in FTP

[Amos Jeffries]

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   Squid Proxy Cache Security Update Advisory SQUID-2023:5
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Advisory ID:       | SQUID-2023:5
Date:              | October 22, 2023
Summary:           | Denial of Service in FTP
Affected versions: | Squid 5.0.3 -> 5.9
                    | Squid 6.x -> 6.3
Fixed in version:  | Squid 6.4
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Problem Description:

  Due to an Incorrect Conversion between Numeric Types
  bug Squid is vulnerable to a Denial of Service
  attack against FTP Native Relay input validation.

  Due to an Incorrect Conversion between Numeric Types
  bug Squid is vulnerable to a Denial of Service
  attack against ftp:// URL validation and access control.

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Severity:

  This problem allows a remote client to perform Denial of Service
  when sending ftp:// URLs in HTTP Request messages or constructing
  ftp:// URLs from FTP Native input.

  This issue is triggered during access control security checks,
  meaning clients may not have been permitted to use the proxy yet.

  FTP support is always enabled and cannot be disabled completely.

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 6.4.

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

Squid 6:
  <http://www.squid-cache.org/Versions/v6/SQUID-2023_5.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:

  Squid older than 5.0.3 are not vulnerable.

  All Squid-5.0.4 up to and including 5.6 are vulnerable.

  All Squid-6.x up to and including 6.3 are vulnerable.

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Workaround:

  * The FTP Native Relay input validation vector can be secured by
    removing all ftp_port directives from squid.conf.

  * There are no workarounds to avoid the ftp:// URL validation and
    access control vector.

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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:

  2023-10-12 11:53:02 UTC Initial Report
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